$40$ men can finish a work in $60$ days. After they work for $20$ days, $20$ more men join them. The total…
$40$ men can finish a work in $60$ days. After they work for $20$ days, $20$ more men join them. The total time from start in which the work is completed is:
$40$ days
$\dfrac{140}{3}$ days
$48$ days
$50$ days
Solution
Total work $= 40 \times 60 = 2400$ man-days. In $20$ days, work done $= 800$. Remaining $= 1600$ man-days. With $60$ men: $\dfrac{1600}{60} = \dfrac{80}{3}$ more days. Total $= 20 + \dfrac{80}{3} = \dfrac{60 + 80}{3} = \dfrac{140}{3}$ days.