Question : A and B can do a piece of work in 72 days. B and C can do it in 120 days and A and C can do it in 90 days. A alone can do it in:
Option 1: 120 days
Option 2: 130 days
Option 3: 150 days
Option 4: 100 days
Latest: SSC CGL preparation tips to crack the exam
Don't Miss: SSC CGL complete guide
Correct Answer: 120 days
Solution :
Given:
Time taken by A and B to do the work = 72 days
⇒ Part of work done by A and B in a day = $\frac{1}{72}$
Time taken by B and C to do the work = 120 days
⇒ Part of work done by B and C in a day = $\frac{1}{120}$
Time taken by A and C to do the work = 90 days
⇒ Part of work done by A and C in a day = $\frac{1}{90}$
⇒ Part of work done by A, B, and C in a day = $\frac{1}{2}[\frac{1}{90}+\frac{1}{120}+\frac{1}{72}]$ = $\frac{1}{2}[\frac{4+3+5}{360}]$ = $\frac{1}{60}$
So, part of work done by A alone = $\frac{1}{60}$–$\frac{1}{120}$ = $\frac{1}{120}$
Therefore, the time taken by A alone to do the work = 120 days
Hence, the correct answer is 120 days.
Related Questions
Know More about
Staff Selection Commission Combined Grad ...
Answer Key | Eligibility | Application | Selection Process | Preparation Tips | Result | Admit Card
Get Updates Brochure
Your Staff Selection Commission Combined Graduate Level Exam brochure has been successfully mailed to your registered email id “”.
