Multiple choice

A is 60% more efficient than B. If A takes 9 days less than B to do a certain piece of work, then find the number of days it would take them to complete the same work, if both work together.

  1. 6 8 13 days

  2. 8 4 13 days

  3. 9 days

  4. 9 3 13 days

  5. None of these

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

If B takes t days, A takes t/1.6 days. Their time difference is 9, so t/1.6 = 15 and t = 24. Their combined rate is 1/15 + 1/24 = 13/120, so the joint time is 120/13 = 9 3/13 days.