Page 152 - Start Up Mathematics_5

Example 9: Find 15% of 70.

Solution: 15% of 70 = 15 × 70 = 105 = 10.5
100 10
Example 10: 20% of 150 apples are rotten. How many apples are rotten?

Solution: Number of rotten apples = 20% of 150

= 20 × 150 = 30 A Challenge!
100 1
So, 30 apples are rotten. What is 33 % of 96?
3
Example 11: What is 25% of 18 kg?

Solution: 25% of 18 kg = 25 × 18 = 450 = 4.5 kg
100 100
So, 25% of 18 kg is 4.5 kg.

Example 12: What is 40% of ` 350?

Solution: 40% of ` 350 = 40 × 350 = 4 × 35 = 140
100

So, 40% of ` 350 is ` 140.
Example 13: If 60% of 1,250 students are girls, how many are boys?

Solution: Number of girls = 60% of 1,250

= 60 × 1,250 = 6 × 125 = 750
100
Number of boys = 1,250 – 750 = 500
So, the number of boys is 500.

To express a number as percentage of another number, divide the given number by the
total number and multiply the result by 100.

Example 14: If 16 out of 80 oranges are spoilt, what percentage of oranges are spoilt?
Solution: Total number = 80
2
Percentage of spoilt oranges = 16 × 100 = 20%
80
So, 20% oranges are spoilt.

EXERCISE 11.2

1. Find the value of the given numbers.

(a) 10% of 62 (b) 22% of 145 (c) 68% of 96
(d) 34% of 138 (e) 82% of 346 (f) 73% of 204

144