Multiple choice

A and B can do work in 12 days .B and C in 15 days and C and A in 20 days.They all work together for 6 days and then A left.In how many more days can B and C finish the remaining work?

  1. 4 days

  2. 5 days

  3. 6 days

  4. 8 days
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A+B's rate: 1/12, B+C's rate: 1/15, C+A's rate: 1/20. Adding all: 2(A+B+C) = 1/12+1/15+1/20 = 12/60 = 1/5, so A+B+C's rate = 1/10. In 6 days, they complete 6/10 = 3/5 of work. Remaining 2/5 is done by B+C at rate 1/15, so time = (2/5)/(1/15) = 6 days.

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