Question

If 20 men working 7 hours a day can do a piece of work in 10 days, in how many days will 15 men working 8 hours a day do the same piece of work ?

• A. $15\frac{5}{21}$
• B. $11\frac{2}{3}$
• C. $6\frac{9}{16}$
• D. $4\frac{1}{5}$

Answer 1

The correct option is B $11\frac{2}{3}$

20 men working 7 hours a day can complete the work in 10 days
20 men working 1 hour a day can complete the work in (10 x 7) days (Less hours $\Rightarrow$ More days)
1 man working 1 hour a day can complete the work in ( 10 x 7 x 20) days (Less men $\Rightarrow$ More days)
1 man orking 8 hours a day can complete the work in $=\frac{(10\times 7\times 20)}{8\times 15}$ days (More men $\Rightarrow$ Less days)
(Less men $\Rightarrow$ More days) = $=\frac{35}{3}$ days = $11\frac{2}{3}$ days