Multiple choice general knowledge math & puzzles

A works thrice as much as B. If A takes 60 days less than B to do a work then find the number of days it would take to complete the work if both work together?

  1. 18.5 days

  2. 20.5 days

  3. 22.5 days

  4. 18 ways

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

Let B take x days, then A takes x/3 days. The difference is x - x/3 = 60, so 2x/3 = 60, meaning x = 90. B takes 90 days and A takes 30 days. Working together, their rate is (1/90 + 1/30) = 4/90. Days taken = 90/4 = 22.5 days.