A casting is made up of Copper and Zinc. If 65% of the casting is
MATHEMATICS
WAEC 2010
A casting is made up of Copper and Zinc. If 65% of the casting is Zinc and there are 147g of Copper. What is the mass of the casting?
- A. 320g
- B. 420g
- C. 520g
- D. 620g
Correct Answer: B. 420g
Explanation
%Zinc + %Copper = 100%
65% + %Copper = 100%
%Copper = 100% - 65% = 35%
%Copper = \(\frac{\text{Mass of % Copper}}{\text{Mass of Casting}}\) x 100%
Mass of Casting = \(\frac{147}{35}\) x 100%
= 420g
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