Question

If $20$ persons can do a piece of work in $7$ days, then the number of persons required to complete the work in $28$ days.

• A. $4$
• B. $5$
• C. $14$
• D. $10$

Answer 1

Answer: (B)

$5$

If A can do a piece of work in $x$ days then A's one days work is $\frac{1}{x}$

Hence $20$ people can do a piece of work in $7$ days

$20$ people's one days work is $\frac{1}{7}$

$1$ persons $1$ days work is $\frac{1}{7\times 20}=\frac{1}{140}$

Therefore $1$ person can do a piece of work in $140$ days

In $28$ days$\frac{140}{28}=5people$ can work