Page 110 - ICSE Math 7

7. What per cent is:
(a) ` 20 of ` 200 (b) 80 p of ` 4 (c) 25 cm of 5 m (d) 20 s of 4 min

8. What percentage of 440 kg is 44 kg?
9. What percentage of ` 300 is equal to 8% of 5,000 p?
10. In a class, 75% students like shakes and the rest of them like juices. Total number of students in
the class is 60. Find the number of students who like juices.
11. Find 85% of 7,500 kg.
12. Find the number whose 64% is 512.
13. To pass an examination, 33% out of a total of 1,200 marks is required. If Anuj just cleared the
exam, find the marks scored by him.

Increase or Decrease in Percentage

To find an increase or decrease of a quantity in percentage, we first find the increase or decrease in
its value, divide it by the original value and then multiply by 100% to get the required percentage.
Increase in value
Increase in percentage = × 100%
Original value Maths Info
Decrease in value Error
Decrease in percentage = × 100% Percentage error = × 100 %
Original value Actual value
Increase in percentage
So, Increase in value = × Original value
100%

∴ New value = Original value + Increase in value
Increase in percentage
= Original value + × Original value
100%
= Original value (1 + percentage as a fraction)
Similarly, new value in the case of decrease in percentage is given by
New value = Original value (1 – percentage as a fraction)

Example 8: Find the increase or decrease in percentage when:
(a) a weight of 75 kg is reduced to 70 kg.
(b) price of diesel increases from ` 60 per litre to ` 62 per litre.
Solution: (a) As the weight is reduced, therefore

Original weight – Reduced weight
Decrease in percentage = × 100 %
Original weight
(75 – 70)
= 75 × 100%
5 2
= × 100% = 6 %
75 3
(b) As the price of diesel is increased, therefore
Increased price – Original price
Increase in percentage = × 100%
Original price
(62 – 60) 2
= 60 × 100% = 60 × 100%

1
= 3 % = 3.33%
3

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