A can do a piece of work in 4 hours; B and C together can do it in 3 hours, while A and C together can do it in 2 hours. B alone can do in:

by

A. 6 hours
B. 13 hours
C. 12 hours
D. 15 hours

🧠 Explanation (Math):

Given: A in 4 h; (B+C) in 3 h; (A+C) in 2 h; find B alone
Step 1: Rates: A=1/4, B+C=1/3, A+C=1/2
Step 2: C = (A+C) − A = 1/2 − 1/4 = 1/4
Step 3: B = (B+C) − C = 1/3 − 1/4 = 1/12
Step 4: Time(B) = 1 ÷ (1/12) = 12 h
Final Answer: 12 hours