Correct Answer - Option 3 : 48
Given:
Time taken by (A + B) to complete the work = 15 days
No. of days worked by A alone = 4 days
No. of days worked by B alone = 20 days
Concept used:
Work done in both cases will be the same.
Formula used:
Total Work done = Efficiency × No. of days worked
Calculation:
Let the efficiency of A and B be a and b.
According to the question,
⇒ (a + b) × 15 = a × 4 + b × 20
⇒ 15a + 15b = 4a + 20b
⇒ 11a = 5b
⇒ a/b = 5/11
Now, total work done = (5 + 11) × 15
⇒ 16 × 15
⇒ 240
No of days required by A to finish the work = Total Work/Efficiency of A
⇒ 240/5
⇒ 48 days.
∴ The A alone can complete the work in 48 days.