Question

If $12$ boys earn $\mathrm{Rs}.840$ in $7$ days, what will $15$ boys earn in $6$ days?

Answer 1

Apply the unitary method to find earning of a boy per day.

Amount earned by $12$ boys in $7$ days is $\mathrm{Rs}.840$.

$\Rightarrow$ Amount earned by $12$ boys in $1$ day is $\frac{840}{7}=\mathrm{Rs}.120$.

$\Rightarrow$ Amount earned by $1$ boy in $1$day is $\frac{120}{12}=\mathrm{Rs}.10$.

$\Rightarrow$ Amount earned by $1$ boy in $6$ days is $10\times 6=\mathrm{Rs}.60$

$\Rightarrow$ Amount earned by $15$ boys in $6$ days is $60\times 15=\mathrm{Rs}.900$.

Therefore, the amount earned by $15$ boys in $6$ days is $\mathrm{Rs}.900$.