Question

An alloy is composed of nickel, zinc, and copper in a7:2:9 ratio. How many kilograms of each metal are needed to make 3.8 kg of this alloy?

Answer 1

let coefficient of the ratios be X
then,
7 x + 2 X + 9 x = 3.8 kg
18 x = 3.8 kg
X = 3.8 / 18

kilograms of :-
Nickel = 1.478 kg
zinc = 0.422 kg
copper = 1.9 kg

Answer 2

Nickel : Zinc : Copper = 7 : 2 : 9

Define x:

Let x be the constant ratio

Nickel : Zinc : Copper = 7x : 2x : 9x

Solve x:

7x + 2x + 9x = 3.8 kg

18x = 3.8 kg

x = 19/90 kg

Find the weight of each metal:

Nickel = 7x = 7(19/90) = 1.48 kg

Zinc = 2x = 2(19/90) = 0.42 kg

Copper = 9x = 9(19/90) =  1.9 kg

Answer: 1.48 kg of Nickel, 0.42 kg of Zinc and 1.9 kg of Copper