Page 108 - ICSE Math 7

Expressing One Quantity as a Percentage of the Other

To express a quantity as a percentage of the other quantity of the same kind, divide the first quantity
12
by the second and then multiply by 100%. Example: 12 h as a per cent of 48 h = × 100%
1 48
= × 100% = 25%.
4
Finding Percentage of a Given Quantity

To find a specific percentage of a given quantity express the given percentage as a fraction of 100 and
48
then multiply it by the given quantity. Example: 48% of ` 200 = × ` 200 = ` 96
100
Example 3: What percentage of 400 g is equal to 10% of 1 kg?
Solution: Let the required percentage be x.

x% of 400 g = 10% of 1 kg
x × 400 g = 10 × 1,000 g
100 100
⇒ 4x = 100 ⇒ x = 25
Thus, 25% of 400 g is equal to 10% of 1 kg.

Example 4: Anita spends 22% of her salary on shopping and 20% on food. Find her savings, if her
salary is ` 52,000.
Solution: Money spent on shopping = 22% of ` 52,000

 22 
= `  × 52 000,  = ` 11,440
 100 
Money spent on food = 20% of ` 52,000
 20 
= `  100 × 52 000,  = ` 10,400


Total money she spent on shopping and food = ` 11,440 + ` 10,400 = ` 21,840
∴ Money saved = ` 52,000 – ` 21,840 = ` 30,160
Alternatively,
Money saved = (100 – 22 – 20)% of ` 52,000
= 58% of ` 52,000

 58 
= `  100 × 52 000,  = ` 30,160


Finding the Number from a Given Percentage of the Number

Write the given percentage as a fraction of 100 and then divide the Maths Info
given number by this fraction to get the required number.
100% of a number is the number
Example 5: Find the number whose 22% is 286. itself.
 22 
Solution: Required number = 286 ÷  
 100

286 × 100
= = 1,300
22

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