Multiple choice

If Person A could build a wall in 4 days and Person B can break the same wall in 5 days find the time taken to break the entire wall if both are working together.

  1. 40 days

  2. 20 days

  3. 12 days

  4. 10 days

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

A builds 1/4 of the wall per day, B breaks 1/5 per day. Working together, net rate = 1/4 - 1/5 = 1/20 per day. Time to break entire wall = 20 days. This is calculated as total work (1 unit) divided by net rate.