Debasing the Coinage
How much lighter will £5 worth of 5p's be with these new lighter coins?
Age
11 to 14
Challenge level
Problem
In 1990 a new size 5p coin was minted. The old size weighed 5.65g while the new size weighs 3.25g.
How much lighter will your pocket be if it contains £5 worth of the new size coins instead of the old size?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
Student Solutions
Answer: 240g
There are 100 5p's in £5.
The old coins weighed $100 \times 5.65 = 565$g, while the new coins weigh $100 \times 3.25 = 325$g.
So your pocket is $565-325=240$g lighter.