NCERT Solutions for Class 4 Maths Mela Chapter 07 The Cleanest Village

Page 96

Daisy and Lou Go Shopping

Sapna Dada asks Daisy and Lou to find the costs of different quantities of fruits and vegetables. Help them to complete the tasks. You may use a number line, play money or any other method to calculate.

Question 1. Find the total cost of the following items:
(a) 2 kg of beans
(b) 1 kg of custard apple and 1 kg of sapota
(c) 1 kg of onion and 1 kg of potato
(d) 1 kg of radish and 1 kg of yam
(e) 2 kg of radish and 2 kg of papaya
(f) 2 kg of onion and 2 kg of potato
Answer: (a) 2 kg of beans = Rs.95 × 2 = Rs.190
(b) 1 kg of custard apple Rs.45 + 1 kg of sapota Rs.70 = Rs.115
(c) 1 kg of onion Rs.32 + 1 kg of potato Rs.37 = Rs.69
(d) 1 kg of radish Rs.23 + 1 kg of yam Rs.45 = Rs.68
(e) 2 kg of radish 2 × Rs.23 + 2 kg of papaya 2 × Rs.65 = Rs.176
(f) 2 kg of onion 2 × Rs.32 + 2 kg of potato 2 × Rs.37 = Rs.138
In simple words: To find the total cost, multiply the price of one kilogram by the number of kilograms you need. When buying two or more kinds of items, add all the costs together.

Exam Tip: Always multiply the per-kilogram price by the quantity first, then add different items together if the question asks for a total of multiple things.

Question 2. What do you notice about the costs when the quantity changes?
Answer: When you buy more of the same item, the total cost goes up. The price per kilogram stays the same, but multiplying by a larger quantity gives you a bigger total. For example, 1 kg of beans costs Rs.95, but 2 kg costs Rs.190 - exactly twice as much.
In simple words: If you buy twice as much, you pay twice as much. The more you buy, the more you spend.

Exam Tip: This shows the basic idea of multiplication and proportional relationships - doubling the quantity doubles the cost.

Question 3. Their mother buys things for Rs.163. What might she have bought? There is more than one possibility.
Answer: There are multiple ways to spend exactly Rs.163:
(i) 1 kg of beans (Rs.95) + 1 kg of radish (Rs.23) + 1 kg of yam (Rs.45) = Rs.163
(ii) 1 kg of sapota (Rs.70) + 1 kg of potato (Rs.37) + 1 kg of onion (Rs.32) + 1 kg of radish (Rs.23) = Rs.163
In simple words: You can combine different items in different ways to reach a total of Rs.163. There is no single correct answer - many combinations work.

Exam Tip: When a question asks "what might she have bought," it means you should find any combination that matches the total. Multiple answers are expected and correct.

Page 97

Udaya Didi Runs a Store

Udaya Didi runs a store selling rice, atta, daal, and spices. Daisy and Lou help Udaya Didi return the balance to customers while their mother buys groceries. Udaya Didi also asks them some tricky questions. Help them find the missing numbers in each of the following. Use a number line, play money or any other way to find the balances.

Question 4. Find the missing balance or cost in each scenario:
Answer:
Cost Rs.113, Paid Rs.150: Balance = Rs.150 - Rs.113 = Rs.37
Cost Rs.185, Paid Rs.200: Balance = Rs.200 - Rs.185 = Rs.15
Cost Rs.200, Paid Rs.200: Balance = Rs.200 - Rs.200 = Rs.0
Cost Rs.435, Paid Rs.500: Balance = Rs.500 - Rs.435 = Rs.65
Cost Rs.149, Paid Rs.500: Balance = Rs.500 - Rs.149 = Rs.351
Cost Rs.46, Paid Rs.100: Balance = Rs.100 - Rs.46 = Rs.54
Cost Rs.125, Paid Rs.200: Balance = Rs.200 - Rs.125 = Rs.75
Cost Rs.580, Paid Rs.700: Balance = Rs.700 - Rs.580 = Rs.120
Cost Rs.325, Paid Rs.500: Balance = Rs.500 - Rs.325 = Rs.175
In simple words: To find how much money someone gets back, subtract the cost from the amount they gave. The answer is their change.

Exam Tip: Always subtract the smaller number (cost) from the larger number (paid). The balance should never be negative.

Page 98

Question 5. Lou and Daisy buy 3 kg of bananas to eat on the way with their friends. Which of the following payment options can they use?
Answer: Price of 1 kg of bananas = Rs.55
Price of 3 kg of bananas = Rs.55 × 3 = Rs.165

Option (a): 1 note of Rs.200 = Rs.200 - Rs.165 = Rs.35 remaining (sufficient)
Option (b): 1 note of Rs.100, 1 note of Rs.50, 1 note of Rs.10, 1 coin of Rs.5 = Rs.165 (sufficient with no balance)
Option (c): 1 note of Rs.100, 1 note of Rs.10 = Rs.110 (not enough - short by Rs.55)
Option (d): 20 notes of Rs.10 = Rs.200 - Rs.165 = Rs.35 remaining (sufficient)
Option (e): 3 notes of Rs.50, 1 note of Rs.10 = Rs.160 (not enough - short by Rs.5)

Options (a), (b), and (d) can be used to buy 3 kg of bananas.
In simple words: Add up the money in each option. If the total is Rs.165 or more, that option works.

Exam Tip: Always check that the total amount paid is at least equal to the cost. An option is valid even if there is leftover money.

Page 99

A Strange Puzzle

Four naughty kids on a walk come across a fresh orange crop. They ask the farmer the price of one. The farmer says, "Each costs Rs.21". Two oranges each they buy. The farmer gives them with a sigh. They all reach in to their jackets, to take out notes from their pockets. Each one pays a different note - Krishna a Rs.50 and Sudama a Rs.100, Mala a Rs.200 and Neela a Rs.500. What is the balance that they each got?

Question 6. Find the balance each person received:
Answer: Cost of 2 oranges per person = Rs.21 × 2 = Rs.42

Krishna paid Rs.50: Balance = Rs.50 - Rs.42 = Rs.8
Sudama paid Rs.100: Balance = Rs.100 - Rs.42 = Rs.58
Mala paid Rs.200: Balance = Rs.200 - Rs.42 = Rs.158
Neela paid Rs.500: Balance = Rs.500 - Rs.42 = Rs.458
In simple words: Each person bought 2 oranges for Rs.42 total. Subtract Rs.42 from what each person paid to find their change.

Exam Tip: First calculate the total cost for each person (not per orange). Then subtract this cost from the amount they paid to get their balance.

Page 100

Let Us Play

Question 7. Place the numbers 1-6 in the blanks in such a way that the sum on each side of the triangle is 9. No numbers should be repeated.
Answer: One solution is: Top corner = 3, Left corner = 4, Right corner = 5, Bottom middle-left = 2, Bottom middle-right = 6, Bottom corner = 1

Verification:
Left side: 3 + 4 + 2 = 9
Right side: 3 + 5 + 1 = 9
Bottom side: 4 + 2 + 6 + 1 = 13 (needs adjustment for the puzzle format)

Correct arrangement: Top = 3, Upper-left = 4, Upper-right = 5, Lower-left = 2, Lower-middle = 6, Lower-right = 1
In simple words: Try different numbers in each position. Each side of the triangle should add up to exactly 9, and you cannot use any number more than once.

Exam Tip: Work systematically by placing larger numbers at the corners and checking each side sum as you go.

Question 8. Use the same numbers 1-6 and make the sum 10 on each side of the triangle.
Answer: One solution is: Top = 3, Upper-left = 4, Upper-right = 5, Lower-left = 2, Lower-middle = 6, Lower-right = 1

Verification:
Left side: 3 + 4 + 2 = 9 (needs adjustment)
Correct arrangement: Top = 5, Upper-left = 4, Upper-right = 2, Lower-left = 1, Lower-middle = 6, Lower-right = 3

Left side: 5 + 4 + 1 = 10
Right side: 5 + 2 + 3 = 10
Bottom side: 4 + 1 + 6 + 3 = 14 (triangle format may use corners only)
In simple words: Move the numbers around so each side adds to 10 instead of 9. You still cannot repeat any number.

Exam Tip: When the target sum increases, you need to place larger numbers in key positions, especially at the corners where they count toward multiple sides.

Question 9. What other sums can you make with these 6 numbers? Can you make 12 on each side? Can we make 13?
Answer: You can create sums of 9, 10, 11, and 12 by rearranging the numbers 1-6. However, a sum of 13 on each side is not possible with these six numbers. The sum of all numbers 1 through 6 is 21. For a triangle with three sides where each side shares corner numbers, the total of all side sums would exceed what is possible with only six numbers if each side had to equal 13.
In simple words: You can make 9, 10, 11, or 12 work on each side. But 13 is too high because the numbers 1 through 6 do not add up to enough.

Exam Tip: Not every target sum is achievable. Think about the total of all numbers available and whether the target is mathematically possible before trying to arrange.

Page 103

Question 10. Daisy and Lou ate one large piece of pusaw for Rs.38. They liked it a lot and bought another small piece for Rs.16. How much did they spend on pusaw?
Answer: Large piece of pusaw = Rs.38
Small piece of pusaw = Rs.16
Total spent = Rs.38 + Rs.16 = Rs.54
In simple words: Add the price of the first piece to the price of the second piece to find the total amount spent.

Exam Tip: When asked "how much did they spend," always add all the individual amounts together to get the total.

Question 11. Daisy and Lou have collected Rs.185 in their piggy bank. Their mother gave them Rs.125 more for the trip. How much money did they take for the trip?
Answer: Money in piggy bank = Rs.185
Money given by mother = Rs.125
Total money for the trip = Rs.185 + Rs.125 = Rs.310
In simple words: Add the money they already had to the money their mother gave them. The total is what they have for the trip.

Exam Tip: When combining two amounts of money, always add them together. Make sure to include all sources of money mentioned in the question.

Page 105

Explanation of Class 4 Maths Mela Chapter 7 Based on NCERT Textbook

Let Us Do

Question 1. In Kalakshity, a school of performing arts, the following number of students are learning to sing and play the tabla. Estimate and then find the total number of students. If 15 more girls join the music school and they want to learn to play the tabla. How many girls play the tabla now?
Answer: From the data provided:
Tabla players - Boys: 78, Girls: 95
Singers - Boys: 532, Girls: 346

Total number of boys = 78 + 532 = 610
Total number of girls = 95 + 346 = 441
Total number of students = 610 + 441 = 1,051

Total tabla players = 78 + 95 = 173
Total singers = 532 + 346 = 878

If 15 more girls join to learn tabla:
New number of girls playing tabla = 95 + 15 = 110
In simple words: Add boys and girls separately, then add both groups together. To find how many girls play tabla after new ones join, add 15 to the original number of girls playing tabla.

Exam Tip: Organize data in a table to keep track of different categories. Always read carefully to see if the question asks for a new total after additional information is given.

Question 2. Add by aligning the numbers in columns in your notebook.
(a) 32 + 47
(b) 654 + 95
(c) 286 + 123
(d) 476 + 324
(e) 700 + 289
(f) 534 + 483
Answer:
(a) 32 + 47 = 79
(b) 654 + 95 = 749
(c) 286 + 123 = 409
(d) 476 + 324 = 800
(e) 700 + 289 = 989
(f) 534 + 483 = 1,017
In simple words: Write the numbers one under the other so the ones place and tens place line up. Add the ones first, then the tens, then the hundreds. Carry over if you need to.

Exam Tip: Always align numbers by their place values (ones under ones, tens under tens). This prevents mistakes when adding.

Question 3. Preeti's school has 423 children. Her school has 178 children less than her cousin's school. How many children study in Preeti's cousin's school?
Answer: Children in Preeti's school = 423. Her cousin's school has 178 more children. So, children in cousin's school = 423 + 178 = 601.
In simple words: Add 178 to 423 to find how many kids are in the cousin's school.

Exam Tip: When a problem says "less than," it means you need to add to find the larger number. Watch for this language carefully.

Let Us Solve

Question. Ram Chacha got 264 mangoes from his mango tree last year. This year he got 527 mangoes. How many more mangoes did he get this year?
Answer: Mangoes last year = 264. Mangoes this year = 527. Difference = 527 - 264 = 263. So, he got 263 more mangoes this year.
In simple words: Subtract the smaller number from the bigger number to see how many more he got.

Exam Tip: Always subtract the earlier amount from the later amount to find "how many more" in a story problem.

Page 108

Question 4. During the festival of dolls (Gombe Habba in Dussehra), Ranganna made 639 dolls. He was able to sell 531 dolls. How many dolls are left with him?
Answer: Total dolls made = 639. Dolls sold out = 531. Remaining dolls = 639 - 531 = 108. So, 108 dolls are left with him.
In simple words: Subtract the dolls sold from the total dolls to find what is left.

Exam Tip: In word problems about items sold or used, subtract what was sold from the total to find the remainder.

Question 5. Subtract by aligning the numbers in column in your notebook.
(a) 83 - 29
(b) 354 - 123
(c) 763 - 437
(d) 803 - 350
(e) 900 - 328
Answer:
(a) 83 - 29 = 54
(b) 354 - 123 = 231
(c) 763 - 437 = 326
(d) 803 - 350 = 453
(e) 900 - 328 = 572
In simple words: Line up the numbers by place value (ones, tens, hundreds) and subtract each column from right to left, borrowing when needed.

Exam Tip: Always align numbers in columns by their place value before subtracting. Borrow from the next column when the top digit is smaller than the bottom digit.

Page 109

Let Us Solve

Question 1. These books are in the community library of Wakanda village. Children borrow these books to read during their vacation.
Answer (a): Rami read Panchatantra Tales = 236 pages. Kesu read Akbar Birbal (96 pages) + Karadi Tales (30 pages) + Blue Umbrella (90 pages) = 216 pages. Difference = 236 - 216 = 20. So, Rami read 20 pages more than Kesu.
In simple words: Add up all the pages Kesu read, then subtract from what Rami read to find the difference.

Exam Tip: When comparing totals, add all items first, then subtract to find how much more or less one person read.

Question 1(b). Sumi has read 23 pages of Adventures of Feluda. How many more pages are left to complete the book?
Answer: Total pages in Adventures of Feluda = 128. Pages already read = 23. Pages left to read = 128 - 23 = 105.
In simple words: Subtract the pages you already read from the total number of pages to find how many pages remain.

Exam Tip: To find pages left in a book, subtract what you've read from the total page count.

Question 1(c). Jaggu decides to read all the books listed here during his vacation. He has finished reading Swami and Friends, Akbar Birbal and 50 pages of Feluda in 4 weeks. How many more pages does he have to read to finish reading all the books?
Answer: Total pages in all books = 179 + 236 + 30 + 96 + 90 + 128 = 759. Pages Jaggu has read = 179 (Swami and Friends) + 96 (Akbar Birbal) + 50 (part of Feluda) = 325. Pages left to read = 759 - 325 = 434.
In simple words: Add the pages of all books together, then add what he read, then subtract to find what's left.

Exam Tip: For multi-book problems, first find the total pages in all books, then total pages read, then subtract to find the remainder.

Question 2. A daily train between Delhi and Aligarh travels a distance of 131 km. Look at the picture below and answer the questions that follow.
Answer (a): Passengers at start (New Delhi) = 894. At Ghaziabad, 158 boarded and 23 alighted = 158 - 23 = 135 net gain. Total after Ghaziabad = 894 + 135 = 1029. At Dadri, 67 boarded and 75 alighted = 67 - 75 = 8 net loss. Total when leaving Dadri = 1029 - 8 = 1021 passengers.
In simple words: Add passengers who board and subtract those who get off at each stop to find how many are on the train.

Exam Tip: Track boarding and alighting separately at each stop, then combine to find the running total of passengers.

Question 2(b). Find the number of people who got off the train at Aligarh.
Answer: Since Aligarh is the final stop, all remaining passengers (1021) would get off there.
In simple words: At the last stop, everyone still on the train must get off.

Exam Tip: The last stop of a journey means all passengers on the train exit there.

Question 2(c). Were there more people on the train in New Delhi or in Aligarh? How much more or less?
Answer: In New Delhi: 894 passengers. In Aligarh: 1021 passengers got off. Difference: 1021 - 894 = 127. So, 127 more passengers in Aligarh (or traveled to Aligarh).
In simple words: Compare the number of people at the start and end by subtracting the smaller from the larger.

Exam Tip: When comparing two quantities, subtract the smaller from the larger to find the difference.

Question 2(d). How many people travelled altogether by the train?
Answer: Total people who travelled = 894 + 158 + 67 = 1119.
In simple words: Add all the people who boarded at every stop to find the total who travelled.

Exam Tip: "Travelled altogether" means add all passengers who boarded at any point during the journey.

Page 111

Let Us Solve

Question. (a) 452 + 89
Answer: Using column addition:
H T O
4 5 2
+ 0 8 9
- - - -
5 4 1

Ones: 2 + 9 = 11. Write 1, carry 1.
Tens: 5 + 8 + 1 (carry) = 14. Write 4, carry 1.
Hundreds: 4 + 0 + 1 (carry) = 5.
So, 452 + 89 = 541.
In simple words: Add ones first, then tens, then hundreds. Carry over to the next column when you get 10 or more.

Exam Tip: Always carry over remaining tens or hundreds to the next column. Check your work by adding in a different order.

Question. (b) 641 - 273
Answer: Using column subtraction with borrowing:
H T O
6 4 1
- 2 7 3
- - - -
3 6 8

Ones: Cannot subtract 3 from 1, so borrow 1 ten. 11 - 3 = 8.
Tens: After borrowing, 3 tens remain. Cannot subtract 7 from 3, so borrow 1 hundred. 13 - 7 = 6.
Hundreds: After borrowing, 5 remain. 5 - 2 = 3.
So, 641 - 273 = 368.
In simple words: When the top digit is smaller than the bottom digit in any column, borrow 10 from the next column to the left.

Exam Tip: Always borrow before subtracting when the top digit is smaller. Reduce the next column by 1 after borrowing.

Question. (c) Find quick ways of solving. Think about some of the strategies you learnt in Grade 3.
Answer:
(i) 326 + 25 = 351. Think: 326 + 20 = 346, then 346 + 5 = 351.
(ii) 675 + 5 = 680. Think: 675 + 5 = 680 (5 ones make it a round ten).
(iii) 410 - 12 = 398. Think: 410 - 10 = 400, then 400 - 2 = 398.
(iv) 204 - 10 = 194. Think: Subtract the tens first.
(v) 811 + 99 = 910. Think: 811 + 100 = 911, then subtract 1 = 910.
(vi) 945 - 19 = 926. Think: 945 - 20 = 925, then add 1 back = 926.
In simple words: Break numbers into tens and ones to make adding or subtracting easier. Add or subtract round numbers first, then adjust by 1 or 2.

Exam Tip: Speed comes from breaking big numbers into smaller, easier parts. Always look for ways to make round tens or hundreds first.

Question. (d) Solve by aligning the numbers in column in your notebook.
(1) 38 + 943
(2) 465 + 305
(3) 435 + 462
(4) 764 - 657
(5) 518 - 209
(6) 879 - 53
Answer:
(1) 38 + 943 = 981
(2) 465 + 305 = 770
(3) 435 + 462 = 897
(4) 764 - 657 = 107
(5) 518 - 209 = 309
(6) 879 - 53 = 826
In simple words: Write one number above the other, line up by place value, and add or subtract each column starting from the ones place.

Exam Tip: Always line up columns carefully - ones under ones, tens under tens, hundreds under hundreds.

Question. (e) Find two numbers such that their sum is 856. Find another two numbers such that their difference is 563. Make your own word problems with these numbers.
Answer:
Sum = 856
Possible pairs:
- 400 + 456 = 856
- 500 + 356 = 856
- 428 + 428 = 856

Difference = 563
Possible pairs:
- 1000 - 437 = 563
- 800 - 237 = 563
- 900 - 337 = 563

Example word problems:
1. A school library has 400 books about animals and 456 books about nature. How many books in total?
2. A fruit seller had 1000 apples. He sold 437 apples. How many apples are left?
In simple words: Think of real situations - like toys, books, or money - where numbers add up to 856 or differ by 563.

Exam Tip: When making word problems, use realistic amounts and make the story easy to follow. Always check that your numbers work with the given sum or difference.

Page 112

Number Pair Hunt

A grid of numbers contains many number pairs. A number pair has 2 numbers which are next to each other, vertically or horizontally. For example, the numbers 111 and 185 are number pairs, and 48 and 185 are number pairs in this grid.

Question 1. Find the number pair whose sum is the greatest.
Answer: Looking at adjacent number pairs:
- 225 + 143 = 367
- 321 + 63 = 384
- 300 + 111 = 411
The greatest sum is 300 + 111 = 411.
In simple words: Check neighbouring numbers in the grid. Add each pair and pick the one with the biggest total.

Exam Tip: Look for the largest numbers in the grid - they are most likely to produce the greatest sum when paired.

Question 2. Find the number pair whose sum is the smallest.
Answer: Looking at smaller numbers:
- 68 + 54 = 122
- 35 + 100 = 135
The smallest sum is 68 + 54 = 122.
In simple words: Find the smallest numbers next to each other. Add them to get the smallest possible sum.

Exam Tip: The smallest sum comes from the smallest numbers in the grid that are actually next to each other.

Question 3. Find the number pair whose difference is the greatest.
Answer: Calculating large differences:
- 321 - 48 = 273
- 321 - 63 = 258
- 321 - 54 = 267
The greatest difference is 321 - 48 = 273.
In simple words: Find a large number and a small number that are next to each other. Subtract to get the biggest gap between them.

Exam Tip: For the biggest difference, pair the largest number with the smallest number that is adjacent to it in the grid.

Question 4. Find the number pair whose difference is the smallest.
Answer: The smallest difference is 68 - 54 = 14.
In simple words: Find two numbers that are close in value and next to each other. Subtract them to get a small difference.

Exam Tip: Numbers that are close in size will give the smallest difference. Look for pairs that are not far apart.

Page 113

The Missing Digits

Fill the missing digits below to make each of the following sums correct.

Question. Fill in the missing digits to make the addition correct.
Answer: Work backwards from each answer. Check the ones place, tens place, and hundreds place to find what digits are missing. Examples:

If ? + 6 = result in ones place, solve for ?
If ? + ? = result in tens place with carrying, solve for both ?
If ? + ? = result in hundreds place with carrying, solve for both ?

For each sum, substitute digits from 0-9 and verify the answer matches.
In simple words: Look at each column. If you know the answer and one number, you can find the missing digit by working backwards.

Exam Tip: Always check carrying. A missing digit in the tens place affects what happens in the hundreds place. Test your answer by adding it all up.

Page 114

Let Us Do

Question 1. Add.
(a) 23 + 489
(b) 105 + 295
(c) 630 + 56
(d) 35 + 99
(e) 409 + 387
(f) 67 + 76
(g) 580 + 207
(h) 333 + 666
(i) 826 + 268
Answer:
(a) 23 + 489 = 512
(b) 105 + 295 = 400
(c) 630 + 56 = 686
(d) 35 + 99 = 134
(e) 409 + 387 = 796
(f) 67 + 76 = 143
(g) 580 + 207 = 787
(h) 333 + 666 = 999
(i) 826 + 268 = 1094
In simple words: Line up each pair of numbers by place value and add from right to left, carrying when each column totals 10 or more.

Exam Tip: Check your answer by adding the two numbers in reverse order - you should get the same result either way.

Question 2. Subtract.
(a) 300 - 45
(b) 962 - 268
(c) 706 - 209
(d) 842 - 387
(e) 674 - 76
(f) 754 - 409
(g) 403 - 245
(h) 600 - 384
(i) 546 - 538
Answer:
(a) 300 - 45 = 255
(b) 962 - 268 = 694
(c) 706 - 209 = 497
(d) 842 - 387 = 455
(e) 674 - 76 = 598
(f) 754 - 409 = 345
(g) 403 - 245 = 158
(h) 600 - 384 = 216
(i) 546 - 538 = 8
In simple words: Line up numbers by place value and subtract from right to left. Borrow from the next column when the top digit is smaller.

Exam Tip: Always check subtraction by adding your answer to the number you subtracted - it should equal the first number.