Question:
An alloy contains 40% copper, 32% nickel and rest zinc. Find the mass of zinc in one kg of the alloy.
Solution:
Mass of the alloy $=1 \mathrm{~kg}$
Percentage of copper $=40 \%$
Percentage of nickel $=32 \%$
Percentage of zinc $=\{100-(40+32)\} \%$
= 28%
$\therefore$ Mass of zinc in $1 \mathrm{~kg}$ of alloy $=\left(\frac{28}{100} \times 1\right) \mathrm{kg}$
$=0.28 \mathrm{~kg}=0.28 \times 1000 \mathrm{~g}=280 \mathrm{~g}$