A and B can do a work in 9 days and 12 days respectively. If they work on alternate days starting with A, then in how many days will the work be completed?
Answer & explanation
Correct answer: option 3
We have,
A = 9 days
B = 12 days
Total work = L.C.M of A and B
Total work = 36
Work done by A in one day = \(\frac{36}{9}\) = 4
Work done by B in one day = \(\frac{36}{12}\) = 3
Now, according to the question,
4 + 3 = 7 work done in two days.
Days Work
2 7
5(2 7)5
---------------------
10 35
Remaining (36 - 35 = 1) work is done by A with 4 efficiency
Time taken by A and B to finish the work = 10\(\frac{1}{4}\)days