Samacheer Kalvi Class 5 Maths Solutions Term 3 Chapter 2 Numbers Exercise 2.1

Question 1. Fill in the blanks
(i) Estimation of 27 to its nearest Tens place is -
Answer: When we estimate 27 to the closest tens place, it becomes 30. This is because 27 is closer to 30 than to 20.
In simple words: The number 27 is closer to 30 than to 20.
(ii) Estimation of 65 to its nearest Tens place is -
Answer: To round 65 to the nearest tens place, we look at the units digit. Since it is 5, we round up to 70. The number 65 is exactly halfway, so we always round up.
In simple words: The number 65 rounds up to 70 when estimating to the nearest tens.
(iii) The cost of 1kg pomegranate is Rs. 93. Then the estimated cost is
Answer: The cost of 1 kg of pomegranate is Rs. 93. When we estimate Rs. 93 to the nearest tens, it becomes Rs. 90. This is because 93 is closer to 90 than to 100. Always round down if the units digit is less than 5.
In simple words: Rs. 93 rounded to the nearest ten is Rs. 90.
(iv) Estimation of 76 bananas to its nearest Tens place is -
Answer: Estimating 76 bananas to the nearest tens place means finding the closest multiple of 10. Since 76 is closer to 80 than to 70, the estimation is 80. This helps in quickly getting an approximate count.
In simple words: The number 76 is rounded up to 80 when estimating to the nearest ten.

🎯 Exam Tip: When estimating to the nearest ten, always look at the units digit to decide whether to round up (5 or more) or down (less than 5).

Question 2. There are 27 girls and 38 boys in a class. Find the sum and estimate the sum to its nearest Tens place.
Answer: First, estimate the number of girls: 27 rounds to 30. Next, estimate the number of boys: 38 rounds to 40. Then, find the estimated total sum by adding these rounded numbers together. The estimated sum is \( 30 + 40 = 70 \). This method is useful for quick mental calculations.
In simple words: Round the number of girls (27) to 30, and boys (38) to 40. Add these rounded numbers to get an estimated total of 70.

🎯 Exam Tip: For estimation questions, always round each number first before performing the calculation, unless specified otherwise.

Question 3. If the cost of a geometry box is Rs. 53 and the cost of a note book is 36, then estimate their cost to its nearest Tens place and find the sum. Also, find the difference between the estimated value and the actual value.
Answer: First, let's find the actual total cost. The geometry box costs Rs. 53 and the notebook costs Rs. 36. The actual sum is \( 53 + 36 = 89 \). Now, let's estimate to the nearest tens. Rs. 53 rounds down to Rs. 50, and Rs. 36 rounds up to Rs. 40. The estimated sum is \( 50 + 40 = 90 \). Finally, find the difference between the estimated sum and the actual sum: \( 90 - 89 = 1 \). This difference shows how close the estimation was.
In simple words: The actual total cost is Rs. 89. When rounded to the nearest ten, the estimated total cost is Rs. 90. The difference between them is Rs. 1.

🎯 Exam Tip: Clearly show both the actual calculation and the estimated calculation, then find the difference if required by the question.

Question 4. If Kavitha has 93 pictures and she gave 42 pictures to her friend Neela, then estimate the pictures to its nearest Tens place and find their difference. Also, find the difference between actual value and the estimated value.
Answer: First, calculate the actual number of remaining pictures: Kavitha had 93 and gave away 42, so she has \( 93 - 42 = 51 \) pictures left. Next, estimate the numbers to the nearest tens. 93 rounds to 90, and 42 rounds to 40. The estimated remaining pictures are \( 90 - 40 = 50 \). Finally, find the difference between the estimated and actual remaining pictures: \( 51 - 50 = 1 \). This helps compare the exact result with a quick estimate.
In simple words: Kavitha started with 93 pictures, gave 42 away, leaving 51. When estimated, she had 90 and gave 40, leaving 50. The difference between the actual and estimated remaining pictures is 1.

🎯 Exam Tip: When dealing with multiple steps, perform each step for both actual and estimated values separately before finding their final difference.

Question 5. The cost of a pen is 32. Find the cost of 6 pens and estimate it to its nearest Tens place.
Answer: The cost of one pen is Rs. 32. To find the cost of 6 pens, multiply the cost of one pen by 6: \( 32 \times 6 = 192 \). Now, estimate this total cost to its nearest tens place. Since 192 is closer to 190 than to 200, the estimated cost is Rs. 190. Knowing the total helps with budgeting for many items.
In simple words: Six pens cost Rs. 192. When we round this to the nearest ten, it becomes Rs. 190.

🎯 Exam Tip: Always read the question carefully to ensure you perform all requested calculations, including both the exact answer and its estimation.

Question 6. Arun has 47, Raja has 54. Find the sum and estimate it to its nearest Hundreds place.
Answer: Arun has Rs. 47 and Raja has Rs. 54. First, find their total sum: \( 47 + 54 = 101 \). Next, estimate this sum to the nearest hundreds place. Since 101 is closer to 100 than to 200, the estimated sum is Rs. 100. This is useful for quickly understanding amounts without needing exact figures.
In simple words: Arun and Raja have a total of Rs. 101. When rounded to the nearest hundred, their total is Rs. 100.

🎯 Exam Tip: Distinguish carefully between rounding to the nearest tens and rounding to the nearest hundreds, as the rules for each are different.

Question 7. There are 21 chocolate bars in a packet. Find the number of chocolate bars in 9 such packets and estimate it to its nearest Hundreds place.
Answer: There are 21 chocolate bars in one packet. To find the total number of chocolate bars in 9 packets, multiply the number of bars per packet by 9: \( 21 \times 9 = 189 \). Now, estimate this total to its nearest hundreds place. Since 189 is closer to 200 than to 100, the estimated number of chocolate bars is 200. This helps in quickly estimating larger quantities.
In simple words: 9 packets have a total of 189 chocolate bars. When rounded to the nearest hundred, this is 200 bars.

🎯 Exam Tip: Always perform the primary calculation first, then apply the estimation rule (nearest tens, hundreds, etc.) to the result.

Question 8. 132 peanut candies are shared equally with 12 students. Find the share for one student and estimate it to its nearest Tens place.
Answer: There are 132 peanut candies to be shared among 12 students. To find out how many candies each student gets, divide the total candies by the number of students: \( 132 \div 12 = 11 \). Now, estimate the share for one student to the nearest tens place. Since 11 is closer to 10 than to 20, the estimated number of candies per student is 10. Sharing items equally ensures fairness for everyone.
In simple words: 132 candies shared among 12 students means each gets 11. Rounded to the nearest ten, each student gets 10 candies.

🎯 Exam Tip: In sharing problems, division is the key operation. Remember to apply the rounding rule to the final result of the division.