An alloy contains only zinc and aluminium in the ratio 7:9.If the weight of the alloy is 8kg then find the weight of aluminium?
z = weight of zinc
a = weight of aluminium
z / a = 7 / 9
Multiply both sides by a
z = 7 a / 9
z + a = 8
7 a / 9 + a = 8
7 a / 9 + 9 a / 9 = 8
16 a / 9 = 8
Multiply both sides by 9
16 a = 72
a = 72 / 16 = 8 ∙ 9 / 8 ∙ 2 = 9 / 2 = 4.5 kg
weight of aluminium = 4.5 kg
Proof:
z = 7 a / 9 = 7 ∙ 4.5 / 2 ∙ 4.5 = 7 / 2 = 3.5 kg
weight of zinc = 3.5 kg
z / a = ( 7 / 2 ) / ( 9 / 2 ) = 7 / 9