Multiple choice

Adam, Brandon and Charlie can do a piece of work in 20, 30 and 40 days, respectively. They started working together, but from the first day itself, Adam came to work on alternate days. In how many days would the work be completed?

  1. 8

  2. 12

  3. 15

  4. 16

  5. 20
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Work rates: A=1/20, B=1/30, C=1/40. LCM=120. A=6, B=4, C=3 units/day. Day 1 (A,B,C): 6+4+3=13. Day 2 (B,C): 4+3=7. Cycle of 2 days = 20 units. 120/20 = 6 cycles. Total days = 6 * 2 = 12.

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