Page 90 - Maths Skills - 7

88 Maths

Let’s Attempt

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Example 1: Find: (i) 15% of 2400 kg (ii) 2.5% of 50 kg (iii) 16 % of ` 240
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Solution: (i) 15% of 2400 kg (ii) 2.5% of 50 kg

 15   15   25.   25 
=  of 2400 kg =  × 2400 kg =  × 50 kg =  × 50 kg




 100   100   100   1000 
= 360 kg = 1.25 kg
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(iii) 16 % of ` 240
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 2 
= `  16 % of 240 
 3 

 50   50 240× 
= `  % of 240 = `  3 100×  = ` 40

 3   
Example 2: What per cent of:
(i) 30 metres is 12 metres? (ii) 150 marks is 48? (iii) 25 kg is 3.5 kg?
Solution: (i) Required per cent (ii) Required per cent (iii) Required per cent

 12   48   35. 
=  × 100 % = 40% =  × 100  % = 32% =  × 100  % = 14%

 30   150   25 
Example 3: Find a number whose 8% is 50.
Solution: Let the required number be x.

\ 8% of x = 50

or 8 × x = 50
100
50 100×
or x = = 625
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Hence, the required number is 625.

Exercise 5.3

1. Express each of the following as a ratio in the simplest form.
1 2
(i) 32% (ii) 6 % (iii) 0.35% (iv) 200% (v) 15 %
4 3
(vi) 0.05% (vii) 102% (viii) 15.25% (ix) 1 %
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2. Express each of the following as a decimal.

5 1
(i) 25% (ii) 0.3% (iii) % (iv) 2 % (v) 145%
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3
1
(vi) 1 % (vii) 0.035% (viii) 1.25% (ix) 36%
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