A water tanker service has enough supply for 250 families for 36 days. How many families must be taken off the list so that the same supply lasts 45 days?

Explanation

1. 01

   Families × days is constant: $250 \times 36 = 9{,}000$ family-days.

2. 02

   Families for 45 days = $9{,}000 \div 45 = 200$.

3. 03

   Families to remove = $250 - 200 = 50$.