Amit can finish the work in 15 days, and Baban can finish the same work in 25 days. They work together for 5 days. The rest of the work was finished by Amit and Chetan in 4 days. How much time is required for Chetan to finish this work?
Show answer & explanation
Correct answer: B
Explanation
Given:
Amit completes the work in 15 days
Baban completes the work in 25 days
Amit and Baban work together for 5 days
Amit and Chetan complete the remaining work in 4 days
Amit's 1 day rate = 1/15
Baban's 1 day rate = 1/25
Combined rate of both = 1/15 + 1/25 = 8/75
Work done in 5 days = 5 × 8/75 = 8/15
Remaining work = 1 − 8/15 = 7/15
Amit and Chetan complete 7/15 of the work in 4 days
Combined rate = (7/15) / 4 = 7/60
Amit + Chetan = 1/15 + 1/C
7/60 = 1/15 + 1/C
7/60 = 4/60 + 1/C
3/60 = 1/C
C = 20 days