A and B can complete a certain work in 12 days and 15 days, respectively. They worked together for 5 days. C alone completed the remaining work in 3 days, A and C together can complete the same work in:
Answer & explanation
Correct answer: option 1
Efficiency of A + B = 5 + 4 = 9
Work done in 5 days = (efficiency of A + B) x No. of days
= 9 x 5 = 45
Remaining work = 60 - 45 = 15
This work is done by C alone in 3 days,
Then efficiency of C = \(\frac{work\; done}{no.\; of\; days}\)
= \(\frac{15}{3}\) = 5
Efficiency of A + C = 5 + 5 = 10
Time taken by A and C to complete the work = \(\frac{Total \; work}{efficiency}\)
= \(\frac{60}{10}\) = 6 days