A ratio is a comparison of the sizes of two or more quantities of same kind by division.
The quantities we compare must be in same units.
Both terms of a ratio can be multiplied or divided by the same non zero number.
Write the following comparisons as ratios in simplest form. Compare the First quantity mentioned with the second quantity mentioned.
Example 1 :
A shirt costing €64 to another costing €32
Solution :
Cost of shirts :
= 64 : 32
Highest Common factor of 64 and 32 is 32
= (64/32) : (32/32)
= 2 : 1
So, the simplest form is 2 : 1
Example 2 :
A rock melon of mass 3 kg to a watermelon of mass 9 kg
Solution :
Mass of rock melon : Mass of water melon
= 3 : 9
Highest Common factor of 3 and 9 is 3
= (3/3) : (9/3)
= 1 : 3
So, the simplest form is 1 : 3
Example 3 :
The height of a 1.5m shrub to the height of a 6m tree
Solution :
Given height of a 1.5m shrub and height of a 6m tree
So, shrub to tree = 1.5 : 6
Multiplying both by 10, we get
= 15 : 60
Highest Common factor of 15 and 60 is 15
= (15/15) : (60/15)
= 1 : 4
So, the simplest form is 1 : 4
Example 4 :
A wetsuit costing $175 to a wetsuit costing $250
Solution :
Cost of wet suit :
= 175 : 250
Highest Common factor of 175 and 250 is 25
= (175/25) : (250/25)
= 7 : 10
So, the simplest form is 7 : 10
Example 5 :
The top speed of a car which is 150 km h-1 to the top speed of a formula. One car which is 350 km h-1
Solution :
Ratio of speed :
= 150 : 350
Highest Common factor of 150 and 350 is 50
= (150/50) : (350/50)
= 3 : 7
So, the simplest form is 3 : 7
Example 6 :
A log of length 4m to a stick of length 10cm
Solution :
As both the
measurements are in different units, first make their units same.
1m = 100 cm
4m = 400 cm
Highest Common factor of 400 and 10 is 10
= (400/10) : (10/10)
= 40 : 1
So, the simplest form is 40 : 1
Example 7 :
The height of an insect which is 2mm to the height of a rat which is 10 cm
Solution :
As both the measurements are in different units, first make their units same.
2mm = 0.2cm
So, insect to rat = 0.2 : 10
Multiplying both by 10, we get
= 2 : 100
Highest Common factor of 2 and 100 is 2
= (2/2) : (100/2)
= 1 : 50
So, the simplest form is 1 : 50
Example 8 :
(a) Shorter side of A : Shorter side of B
(b) longer side of A : longer side of B
(c) Area of A : Area of B
Solution :
(a) Shorter side of A : Shorter side of B
= 3 : 6
= 1 : 2
So, the ratio is 1 : 2
(b) longer side of A : longer side of B
= 5 : 10
= 1 : 2
So, the ratio is 1 : 2
(c) Area of A : Area of B
Area of Rectangle A = 5(3)
= 15 cm2
Area of Rectangle B = 10 × 6
= 60cm2
Area of A : Area of B = 15 : 60
= 1 : 4
Example 9 :
IF 2/3 of the workers in an office are non smokers, what is the ratio of smokers to nonsmokers ?
a) 2 : 5 b) 1 : 2 c) 3 : 5 d) 2 : 3
Solution :
From the given fraction, we understand that
2 x = non smoker
3x = total number of workers in the office
Smokers = 3x - 2x
= 1x
Ratio between smokers to non smokers
1x : 2x
= 1 : 2
So, option b is correct.
Example 10 :
If 80% of the applicants to a program were rejected, what is the ratio of the number accepted to the number rejected ?
a) 1/5 b) 1/4 c) 2/5 d) 4/5
Solution :
Total number of applicants to be 100%
80% of the applicants are rejected, then 20% of the applicants can be selected.
Ratio between accepted to rejected = 20 : 80
= 20/80
= 2/8
= 1/4
So, option b is correct.
Example 11 :
If a : b = 3 : 5 and a : c = 5 : 7, what is the ratio of b : c?
a) 21 : 35 b) 21 : 25 c) 25 : 21 d) 35 : 21
Solution :
a : b = 3 : 5 and a : c = 5 : 7
Multiplying the first ratio by 5 and second ratio by 3, we get
a : b = 15 : 25
a : c = 15 : 21
b : a = 25 : 15
b/a = 25/15
c : a = 21:15
c/a = 21/15
b/a = c/a => 25/15 = 21/15
b/c = 25/21
b : c = 25 : 21
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