Correct Answer - Option 1 : 8
A is 50% more efficient than B.
Time taken by B alone = 20 days
Total work = Efficiency × Time
Where Efficiency is work done per day.
The efficiency of A = 150% of the efficiency of B
⇒ The efficiency of A = (3/2) of efficiency of B
⇒ (Efficiency of A)/(Efficiency of B) = 3/2
Now, Total efficiency of (A + B) = 3 + 2 = 5
We know that Time taken by B alone = 20 days.
So, Total work = (Efficiency of B) × (Time taken by B)
⇒ 2 × 20
According to the question,
Time taken by (A + B) to complete the whole work = (Total work)/(Total efficiency)
⇒ 8 days
∴ A and B both working together will complete the whole job in 8 days.