A can complete a certain work in 30 days. He started the work. After 4 days, B joined him and the whole work was completed in 10 days from the beginning. B alone can complete one-third of the same work in:
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 3 days.
A can do a work = 30 days
Let's assume B can do the same work = x days
So, the total work = LCM of 30 and x = 30x
Efficiency of A and B= 30x/30 = x and 30x/x = 30
Now according to the question,
(30x - 4x)/(x + 30) = 6
x = 9
So, the one third work done by B = (30 × 9)/(30 × 3) = 3 days