The document discusses calculating percentage increases and decreases. It provides examples of increasing 130 by 22% and decreasing 120 by 20%. It also discusses calculating percentage change when the first number is increased or decreased to become the second number. The document includes class work and assessment questions involving applying percentages to increase or decrease given values.

1. PERCENTAGES
Percentage increase and
decrease

2. EXPLANATION:
Eg1: Increase 130 by 22%
130 × (100+22)%
= 130 × 122%=130× 122
=130× 1.22=158.6
100
Eg2: Decrease 120 by 20%
120 × (100-20)%
=120 × 80%= 120 × 80
= 120×0.8=96
100

3. EXPLANATION( TYPE 2):
Eg1: The first number is increased to become the second
number .calculate the percentage increase
50 60
Ans: 60 – 50=10 ;
10
Eg2: The first number is decreased to become the second
number .Calculate the percentage decrease.
60 50
Ans: 60 – 50=10 ;
100 16.7%
10
60
 
100 20%
50
 

4. CLASS WORK:
Q1)Increase the following by the given percentage
a) 150 by 25% , b) 70 by 250% c) 230 by 40%
Q2) Decrease the following by the given percentage
a) 120 by 25% , b) 40 by 5% c) 75 by 42%
Q3) A garage increases the price of a truck by 12%. If the
original price was R.O 14500, Calculate its new price

5. CLASS WORK:
In the following questions the first number is increased
to become the second number. Calculate the
percentage increase
a) 75 135 , b) 40 84
In the following questions the first number is decreased to
become the second number. Calculate the percentage
decrease
a) 50 25 , b) 80 56

6. ASSESSMENT
Q) A farmer increases the yield on his farm by 15%.If this
previous yield was 65000 tones, what is his present yield
Homework:
Q) The cost of a computer in a computer store is reduced
by 12.5% in a sale .If the computer was priced at R.O
780,what is its price in the sale?