Question

An alloy of zinc and copper weighs $12\frac{1}{2}kg$. If, in the alloy, the ratio of zinc and copper is $1:4$, find the weight of copper in it.

Answer 1

It is given that zinc and copper are in the ratio $1:4$ and the total weight is $12\frac{1}{2}kg\text{or}12.5kg$
i.e., $12.5kg$ is divided into $1+4=5$ equal parts.
Then, weight of copper will be 4 out of 5 equal parts of $12.5kg$
$=\frac{4}{5}\text{of}12.5kg$
$=\frac{4}{5}\times 12.5=\frac{50}{5}=10kg$
Therefore, the weight of the copper is $10kg$.