Multiple choice

A and B can do a piece of work in 10 days and 20 days, respectively. If they work on alternate days, then find the least number of days in which the work will be completed.

  1. 13

  2. 14

  3. 12

  4. 18

  5. 15

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A does 1/10 of the work per day, and B does 1/20. In a 2-day cycle, they complete 1/10 + 1/20 = 3/20 of the work. After 6 cycles (12 days), 18/20 of the work is done; on day 13, A completes the remaining 2/20 (1/10) of the work.