Question

The ratio of weights of zinc and copper in an alloy is $5:8$. If the weight of copper in a sample of this alloy is $12g$, what is the weight of zinc?
[1 Mark]

A. $6.5g$
B. $6g$
C. $7g$
D. $7.5g$

Answer 1

Correct option: D
(1 Mark)

Given,
Ratio of weights of zinc and copper $=5:8$
Let the weight of zinc for $8g$ of copper be $x$.
Using the concept of equivalent ratios,
$\frac{Zinc}{Copper}$ = $\frac{5}{8}$ = $\frac{x}{12}$
<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> ⇒ $x$ $=\frac{5\times 12}{8}$
⇒ $x$ $=7.5g$
$\therefore$ The weight of zinc is $7.5g$.