A can finish 50% of a work in 30 days. He works at it for 15 days and then B alone finishes the remaining work in 30 days. In how many days can A and B working together finish 25% of the whole work?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 6.
Time taken by A to complete the whole work = 30 × 2 = 60 days
Portion of work A finishes in 15 days = 15/60 = 1/4
Remaining work = 1 - 1/4 = 3/4
This 3/4th of the work was completed by B in 30 days
So, the time taken by B to finish the total work = 30 × 4/3 = 40 days
Now, LCM of 60 & 40 = 120
Let us assume that the total work is 120 units.
⇒ 25% of the work = 0.25 × 120 = 30 units
Efficiency of A = 120/60 = 2 units
Efficiency of B = 120/40 = 3 units
Total efficiency of A & B = 2 + 3 = 5 units
Required no. of days = 30/5 = 6 days.