Comparing Quantities Class 8 PPT

 Page 1


Mr. Bloom, Monroe H.S.
COMPARING QUANTITIES
Page 2


Mr. Bloom, Monroe H.S.
COMPARING QUANTITIES
A percentage is a fraction converted to a decimal, and then multiplied 
by 100 and add percent sign (%).
Percentages
Example 1
For example,
100
7
% 7 ?
Change each of the following into percentage.
(a)  0.83
25
12
(b)
Solution :
  
??
(a) 0.83 ? 0.83 ?100% ? 83%
  
??
(b)
12
25
?
12
25
? .48 ?100% ? 48%
Page 3


Mr. Bloom, Monroe H.S.
COMPARING QUANTITIES
A percentage is a fraction converted to a decimal, and then multiplied 
by 100 and add percent sign (%).
Percentages
Example 1
For example,
100
7
% 7 ?
Change each of the following into percentage.
(a)  0.83
25
12
(b)
Solution :
  
??
(a) 0.83 ? 0.83 ?100% ? 83%
  
??
(b)
12
25
?
12
25
? .48 ?100% ? 48%
When an original value is changed to a new value, the
percentage change of the value can be measured in
the following way.
Percentage Change
Page 4


Mr. Bloom, Monroe H.S.
COMPARING QUANTITIES
A percentage is a fraction converted to a decimal, and then multiplied 
by 100 and add percent sign (%).
Percentages
Example 1
For example,
100
7
% 7 ?
Change each of the following into percentage.
(a)  0.83
25
12
(b)
Solution :
  
??
(a) 0.83 ? 0.83 ?100% ? 83%
  
??
(b)
12
25
?
12
25
? .48 ?100% ? 48%
When an original value is changed to a new value, the
percentage change of the value can be measured in
the following way.
Percentage Change
Percentage Change
Example 2
Solution :
% 100
60
60 48
?
?
? change Percentage
Peter’s weight decreases from 60 kg to 48 kg. Find the 
percentage change of his weight.
% 20 ? ?
? Percentage decrease of weight is 20%.
If the answer is positive, it 
means a percentage increase. 
If the answer is negative, it 
means a percentage 
decrease.
Page 5


Mr. Bloom, Monroe H.S.
COMPARING QUANTITIES
A percentage is a fraction converted to a decimal, and then multiplied 
by 100 and add percent sign (%).
Percentages
Example 1
For example,
100
7
% 7 ?
Change each of the following into percentage.
(a)  0.83
25
12
(b)
Solution :
  
??
(a) 0.83 ? 0.83 ?100% ? 83%
  
??
(b)
12
25
?
12
25
? .48 ?100% ? 48%
When an original value is changed to a new value, the
percentage change of the value can be measured in
the following way.
Percentage Change
Percentage Change
Example 2
Solution :
% 100
60
60 48
?
?
? change Percentage
Peter’s weight decreases from 60 kg to 48 kg. Find the 
percentage change of his weight.
% 20 ? ?
? Percentage decrease of weight is 20%.
If the answer is positive, it 
means a percentage increase. 
If the answer is negative, it 
means a percentage 
decrease.
Profit and Loss
The profit and loss in trading refers to the difference between 
the cost price and the selling price.
% 100 ?
?
?
price Original
price Original  price New 
 change Percentage  (1)
The selling price can be found if the cost price and 
the percentage change are given.
) 1
1
percentage Loss price( Cost                             
or ) percentage Profit  ( price Cost  price Selling  (2)
?
? ?