Question

If $20$ men working $8$ hours per day can complete a piece of work in $21$ days. How many hours per day must $48$ men work to complete the same job in $7$ days

• A. $12$
• B. $20$
• C. $10$
• D. $15$

Answer 1

The correct option is C $10$

We know, Work = Men $\times$ hr/day×days

Work is same in both cases

Let $48$ men will complete the same work in $x$ hr/day

$20\times 8$ hr/day $\times 21=48\times x$ hr/day $\times 7$

$48x=\frac{(20\times 8\times 21)}{7}$

$48x=20\times 8\times 3$

$x=\frac{(20\times 8\times 3)}{48}$

$x=\frac{480}{48}$

$x=10$

$48$ men must work $10$ hr/day to complete the same work in $7$ days