Multiple choice

A can do some work in 24 days, B can do it in 32 days and C can do it in 60 days. They start working together. A left after 6 days and B left after working for 8 days. How many more days are required to complete the whole work?

  1. 30

  2. 25

  3. 22

  4. 20
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Work rates: A=1/24, B=1/32, C=1/60. In 6 days, A+B+C do 6*(1/24+1/32+1/60) = 6*(10+7.5+4)/240 = 6*(21.5/240) = 129/240. In next 2 days, B+C do 2*(1/32+1/60) = 2*(15+8)/480 = 46/480 = 23/240. Total work done = 129/240 + 23/240 = 152/240. Remaining work = 88/240. C does this in (88/240) / (1/60) = 88/4 = 22 days.

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