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.
This problem is taken from the UKMT Mathematical Challenges.