Question

Working alone, A can do a job in 15 days and B can do the same job in 18 days. In how many days will the job be completed if both work together?

• A. 10/3 days
• B. 90/11 days
• C. 5/36 days
• D. 15 days

Answer 1

Answer:

B. 90/11 days

$$A can do the job in 15 days,</p><p style="color: rgb(0,0,0); margin-top: 2px; margin-bottom: 2px" data-pxy="true">$$Work done by A in one day $=\frac{1}{15}$

$$B can do it in 18 days</p><p style="color: rgb(0,0,0); margin-top: 2px; margin-bottom: 2px" data-pxy="true">$$Work done by B in one day $=\frac{1}{18}$

Both of them Working together to complete the work in

$(\frac{1}{15}+\frac{1}{18})n=1$

$(\frac{18+15}{18\times{15}})n=1$

Time required to complete the work together,$n=\frac{90}{11}$

$$<u>Alternate Method;</u></p><div style="text-align: left; width: 100$$Efficiency of A and B is 11

$$Both together can complete a work in$\frac{90}{11}days$