CBSE Class 7 Mathematics Decimals Assignment Set 02

Q1. Misha purchased 2.7 m cloth for Rs 97.35. At what rate did she purchased the cloth?
Answer: Total length of cloth = 2.7 m
Total cost of cloth = Rs 97.35
Rate of cloth per metre = \(\frac{97.35}{2.7}\)
\(= \frac{9735}{270}\)
\(= \text{Rs } 36.05\)
In simple words: Divide the total cost by the total length of the cloth to find the cost per metre.

Exam Tip: Remove decimals by multiplying both numerator and denominator by 100 before performing long division to avoid calculation errors.

Q2. Arun sold few bags of rice weighing 585.25 kg. If the weight of one bag is 29.25 kg, find the number of bags sold.
Answer: Total weight of rice sold = 585.25 kg
Weight of one bag of rice = 29.25 kg
Number of bags sold = \(\frac{585.25}{29.25}\)
\(= \frac{58525}{2925}\)
\(= 20 \text{ bags approximately}\)
In simple words: Divide the total weight of rice by the weight of a single bag to get the total number of bags.

Exam Tip: Since both numbers have two decimal places, shift the decimal point two places to the right in both numbers to simplify the division.

Q3. 2.25 kg potatoes cost Rs 19.35. Shewta bought 3.75 kg potatoes. How much change will Shewta get if she gives a 50-rupee note to the shopkeeper?
Answer: Cost of 2.25 kg potatoes = Rs 19.35
Cost of 1 kg potatoes = \(\frac{19.35}{2.25} = \text{Rs } 8.60\)
Cost of 3.75 kg potatoes = \(3.75 \times 8.60 = \text{Rs } 32.25\)
Amount given to the shopkeeper = Rs 50.00
Change received = \(50.00 - 32.25 = \text{Rs } 17.75\)
In simple words: First find the unit cost per kg, calculate the total cost for 3.75 kg, and subtract it from 50 to find the remaining change.

Exam Tip: Always calculate the unit price first in unitary method word problems involving decimals.

Q4. The product of two numbers is 59.328. If one of the number is 12.36, find the other number.
Answer: Product of two numbers = 59.328
Given number = 12.36
Other number = \(\frac{59.328}{12.36}\)
\(= \frac{59328}{12360}\)
\(= 4.8\)
In simple words: Divide the given product by the known number to find the unknown number.

Exam Tip: Make the number of decimal places equal by adding a trailing zero to the divisor before dividing.

Q5. A train covers a distance of 13245.60 km in 31.02 hrs. How much distance will it cover in one hour?
Answer: Total distance covered = 13245.60 km
Total time taken = 31.02 hrs
Distance covered in 1 hour = \(\frac{13245.60}{31.02}\)
\(= \frac{1324560}{3102}\)
\(= 439.8576 \text{ km}\)
In simple words: Divide the total distance by the total hours to find the speed or distance covered per hour.

Exam Tip: Maintain precision up to four decimal places when the division does not terminate early.