Multiple choice

X completes 40% of his work in 12 days. Then takes the help of Y and Z. Y is 50% efficient as X, Z is 50% efficient as Y. In how many more days will they complete the work?

  1. 18 days

  2. 72/7 days

  3. 6 days

  4. 144 days

  5. 72/3 days

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

When X is doing 40 % of work, it takes 12 days.
When X is doing 60% of work, it takes 18 days. When X + Y + Z or X + 1/2X + 1/4X is doing 60% of work it takes 18/(1 + 1/2 + 1/4) = 72/7 days.