Kate's Date
When Kate ate a giant date, the average weight of the dates decreased. What was the weight of the date that Kate ate?
Age
11 to 14
Challenge level
Problem
The mean mass of five giant dates was 50g.
Kate ate one, and the mean mass of the four remaining dates was 40g.
What was the mass of the date that Kate ate?
Student Solutions
The total mass of the original five dates was 5 x 50g = 250g.
The total mass of the four remaining dates was 4 x 40g = 160g.
Therefore the mass of the date that Kate ate was 250g - 160g = 90g.