Multiple choice

X is thrice as good as Y to do a job and is able to complete a work in 30 days less than Y. Working together, they can do the job on the

  1. 25th day

  2. 12th day

  3. 14th day

  4. 11th day

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

Let Y take x days; then X takes x/3 days. Given x - x/3 = 30, we find x = 45 days for Y and 15 days for X. Their combined rate is 1/45 + 1/15 = 4/45, meaning they finish in 45/4 = 11.25 days. They complete the work during the 12th day.