A is capable of completing a task in 10 days, while B can finish the same task in 15 days. A works alone for the first 4 days and is then joined by B. How many total days will it take to complete the entire task?
Show answer & explanation
Correct answer: B
Explanation
Given:
A completes the work in 10 days.
B completes the work in 15 days.
A works alone for the first 4 days.
According to the formula:
Work Rate = 1 / Time
A's work rate per day = 1/10
Work done by A in 4 days = 4/10 = 2/5
Remaining work = 1 − 2/5 = 3/5
Combined work rate of A and B per day
= 1/10 + 1/15
= (3 + 2) / 30
= 5/30
= 1/6
Time = (3/5) ÷ (1/6)
= (3/5) × 6
= 18/5
= 3.6 days
Total time = 4 + 3.6 = 7.6 days