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Question : A and B can do a piece of work in 8 days, B and C can do it in 24 days while C and A can do it in $8\frac{4}{7}$ days. In how many days can C do it alone?

Option 1: 60 days

Option 2: 40 days

Option 3: 30 days

Option 4: 10 days


Team Careers360 24th Jan, 2024
Answer (1)
Team Careers360 25th Jan, 2024

Correct Answer: 60 days


Solution : Given: A and B can do a piece of work in 8 days. B and C can do it in 24 days,  and A and C can do it in $\frac{60}{7}$ days.
(A+B)'s 1 day's work = $\frac{1}{8}$
(B+C)'s 1 day's work = $\frac{1}{24}$
(A+C)'s 1 day's work = $\frac{7}{60}$
Adding the above three equations we get,
2(A+B+C)'s 1 day's work = $\frac{1}{8}+\frac{1}{24}+\frac{7}{60}=\frac{15+5+14}{120} = \frac{34}{120} = \frac{17}{60}$
⇒ (A+B+C)'s 1 day's work is $\frac{17}{120}$.
C's 1 days's work $=\frac{17}{120} - \frac{1}{8} = \frac{17–15}{120} = \frac{2}{120} = \frac{1}{60}$
So, C can alone complete the work in 60 days.
Hence, the correct answer is 60 days.

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