CBSE Class 7 Mathematics Decimals Assignment Set 04

Question 1. Anil earns Rs 27.50 per hour. If he worked 7.5 hours. How much did he earned?
Answer: Earnings per hour = Rs 27.50
Total working hours = 7.5 hours
Total earnings = 27.50 \(\times\) 7.5
\(= 206.25\)
Total amount earned = Rs 206.25
In simple words: Multiply the hourly wage by the total number of hours worked to find the total earnings.

Exam Tip: Count the total number of decimal places in both numbers (two in 27.50 and one in 7.5, making a total of three) and place the decimal point accordingly in the final product.

Question 2. Shanti bough 2.25 m cloth at the rate of Rs 250.95 per metre. Find the cost of the cloth.
Answer: Length of cloth = 2.25 m
Cost of 1 metre of cloth = Rs 250.95
Total cost = 250.95 \(\times\) 2.25
\(= 564.6375\)
Total cost of the cloth = Rs 564.6375
In simple words: Multiply the price per metre by the total length of the cloth bought.

Exam Tip: Be careful with the multiplication of decimals with four total decimal places and keep all digits until the final step before rounding if required.

Question 3. Speed of Ravi is 5.5 km/hour. If he reaches his school in 2.30 hour. Find the distance of the school
Answer: Speed of Ravi = 5.5 km/hour
Time taken = 2.30 hours (or 2.3 hours)
Distance = Speed \(\times\) Time
Distance = 5.5 \(\times\) 2.3
\(= 12.65 \text{ km}\)
Distance of the school = 12.65 km
In simple words: Find distance by multiplying speed by time.

Exam Tip: Remember the formula Distance = Speed \(\times\) Time and ensure units are consistent.

Question 4. A Taxi driver charges Rs 17.25 per km. How much will he charge for a journey of 15.25 km?
Answer: Charge per km = Rs 17.25
Total distance = 15.25 km
Total charge = 17.25 \(\times\) 15.25
\(= 263.0625\)
Rounding to nearest paisa (two decimal places) = Rs 263.06
In simple words: Multiply the rate per kilometre by the total distance of the journey.

Exam Tip: For currency calculations, round off to two decimal places (paise) unless specified otherwise.

Question 5. A Car covers a distance of 19.5 km on one litre of petrol. How far can it go in 25 litres of petrol?
Answer: Distance covered in 1 litre of petrol = 19.5 km
Total petrol available = 25 litres
Total distance = 19.5 \(\times\) 25
\(= 487.5 \text{ km}\)
Total distance covered = 487.5 km
In simple words: Multiply the distance covered per litre by the total number of litres.

Exam Tip: Read word problems carefully to determine whether multiplication or division is required (here, finding total distance from per-litre value requires multiplication).