## RD Sharma Solutions For Class 7 Maths Chapter 10 Unitary Method Free Online

Exercise 10.1 Page No: 10.2

**1. 20 chocolates cost Rs 320. Find the cost of 35 such chocolates.**

**Solution:**

Given cost of 20 chocolates = Rs 320

Cost of 1 chocolate = (320/20)

Therefore, the cost of 35 chocolates = (320/20) × 35

= Rs 560

**2. The cost of 40 meters of cloth is Rs 200. Find the cost of 50 meters of cloth.**

**Solution:**

Given cost of 40 meters of cloth = Rs 200

Cost of 1 meter of cloth = (200/40)

Therefore, the cost of 50 chocolates = (200/40) × 50

= Rs 250

**3. A car can cover a distance of 522 km on 36 liters of petrol. How far can it travel on 14 liters of petrol?**

**Solution:**

Given that number of kilometres a car can cover by using 36 litres of petrol = 522 km

Number of kilometres a car can cover by using 1 litre of petrol = 522/36

Hence, the number of kilometres a car can cover by using 14 litres = (522/36) × 14

= 203 km

**4. Travelling 900 km by rail costs Rs 280. What would be the fare for a journey of 360 km when a person travels by the same class?**

**Solution:**

Given that cost of travelling 900 km by rail = Rs 280

Therefore cost of travelling 1 km by rail = (280/900)

Hence, Cost of travelling 360 km by rail = (280/900) × 360

= Rs 112

**5. If 6 oil tankers can be filled by a pipe in 4(1/2) hours, how long does the pipe take to fill 4 such oil tankers?**

**Solution:**

Given that time taken by 6 oil tankers to be filled by a pipe = 4 (1/2) hours = (9/2) hours

Time taken by 1 oil tankers to be filled by a pipe = (9/2)/6 hours

Hence time taken by 4 oil tankers to be filled by a pipe = (9/2)/6 × 4

= (9/12) × 4

= 3 hours

**6. 3/4 of the salary per month is Rs 600. What is the salary per month?**

**Solution:**

Given that 3/4 of the salary per month = 600

Let the salary of the month be x

Therefore ¾ × x = 600

x = 600 × (4/3)

x = 800

Therefore salary per month is Rs 800

**7. The cost of 32 tables is Rs 23520. Find the number of such tables that can be purchased for Rs 51450.**

**Solution:**

Given that number of tables bought for Rs 23520 = 32

Number of tables bought for Rs 1 = 32/23520

Hence, number of tables bought for Rs 51450 = (32/23520) × 51450 = 70

**8. The yield of wheat from 6 hectares is 280 quintals. Find the number of hectares required for a yield of 225 quintals.**

**Solution:**

Given number of hectares required for a yield of 280 quintals = 6 hectares

Number of hectares required for a yield of 1 quintal = 6/280 hectares

Hence, the number of hectares required for a yield of 225 quintals = 6/280 × 225

= 4(23/28) hectares

**9. Fifteen post cards cost Rs 2.25. What will be the cost of 36 post cards? How many postcards can we buy in Rs 45?**

**Solution:**

Given cost of 15 post cards = Rs 2.25

Cost of 1 post card is = 2.25/15

Hence, the cost of 36 post cards = (2.25/15) × 36

= Rs 5.40

Number of post cards bought for Rs 2.25 = 15

Numbers of post cards bought for Rs 1 = 15/2.25

Hence number of post cards for Rs 45 = (15/2.25) × 45

= 300

**10. A rail journey of 75 km costs Rs 215. How much will a journey of 120 km cost?**

**Solution:**

Given cost of a rail journey of 75 km = Rs 215

Cost of a rail journey of 1 km = 215/75

Hence, cost of a rail journey of 120 km = (215/75) × 120

= Rs 344

**11. If the sales tax on a purchase worth Rs 60 is Rs 4.20. What will be the sales tax on the purchase worth of Rs 150?**

**Solution:**

Given sales tax on the purchase worth of Rs 60 = Rs 4.20

Sales tax on the purchase worth of Rs 1 = Rs 4.2060

Hence, sales tax on the purchase worth of Rs 150 = (4.20/60) × 150

= Rs 10.50

**12. 52 packets of 12 pencils each, cost Rs 499.20. Find the cost of 65 packets of 10 pencils each.**

**Solution:**

Given total number of pencils in 52 packets of 12 pencils each = 52 × 12

= 624 pencils

Also given that cost of 624 pencils = Rs 499.20

Cost of 1 pencil = (499.20/624)

Number of pencils in 65 packets of 10 pencils each = 65 x 10

= 650 pencils

Therefore, cost of 650 pencils = (499.20/624) × 650

= Rs 520.