Problems on Numbers - Quantitative Aptitude (MCQ) questions for Q. 92
Q. A and B working separately can complete a piece of work in 9 and 12 days respectively. If they work alternatively starting from A in how many days will the work be completed?- Published on 15 Jun 15a. 10.25 days
b. 11.5 days
c. 12.75 days
d. 9 days
ANSWER: 10.25 days
A takes 9 days to complete a piece of work. B takes 12 days to complete a piece of work.
=> In one day A came complete 1/9th of the task(x/9)
=> In one day B can complete 1/12th of the job.(x/12)
First day x/9th work will be done next day x/12th and so on:
Together A and B can do x/9 + x/12 work.
=>(x/9) + (x/12) = 7/36th work done
In 10 days 35/36th of the work will be done.
On 11th day it will be A’s chance. It takes A 1 day to complete 1/9th work.
So, 1/36th work will be done in 1/4 days.
=>10.25 days
