Problem 1 :
To make standard concrete, gravel, sand and cement are mixed in the ratio 5 : 3 : 1. I wish to make 18 tonnes of concrete. How much gravel, sand and cement must I purchase?
Solution :
Total parts = 5 + 3 + 1
= 9 parts
Quantity of concrete = 18 tones
Quantity of gravel = 5/9 of 18
= (5/9) ⋅ 18
= 10 tonnes of gravel
Quantity of sand = 3/9 of 18
= (3/9) ⋅ 18
= 6 tonnes of sand
Quantity of cement = 1/9 of 18
= (1/9) ⋅ 18
= 2 tonnes of cement
Problem 2 :
My fortune of $810, 000 is to be divided in the ratio 4 : 3 : 2. How much does each person receive?
Solution :
Let X, Y and Z be three persons.
Total number of parts = 4 + 3 + 2
= 9 parts
Amount received by X = 4/9 of 810 000
= (4/9) ⋅ 810 000
= 360000
Amount received by Y = 3/9 of 810 000
= (3/9) ⋅ 810 000
= 270000
Amount received by Z = 2/9 of 810 000
= (2/9) ⋅ 810 000
= 180000
Problem 3 :
An alloy is made from copper, zinc and tin in the ratio 17 : 2 : 1. How much zinc is required to make 10 tonnes of the alloy?
Solution :
Total number of parts = 17 + 2 + 1
= 20 parts
Quantity of Zinc required = (2/20) of 10 tonnes
= (2/20) ⋅ 10
= 1 tonne
Problem 4 :
Joe and Bob share the cost of a video game in the ratio 3 : 7.
a) What fraction does each pay?
b) If the game costs $35, how much does each pay?
c) If Joe pays $12, how much does Bob pay?
d) If Bob pays $42, what is the price of the video game
Solution :
Total parts = 3 + 7
= 10 parts
(a) Joe will pay 3/10 and Bob will pay 7/10.
(b) Cost of game = $35
Joe has to pay = (3/10) of 35
= (3/10) ⋅ 35
= $10.5
Bob has to pay = (7/10) of 35
= (7/10) ⋅ 35
= $24.5
c) Amount paid by Joe = 3x
3x = 12
x = 4
Amount paid by Bob = 7x
= 7(4)
= $28
d) 7x = 42
x = 6
Price of video game = 10x
= 10(6)
= 60
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