Ram divided $15$ pennies among four small bags.

He labelled each bag with the number of pennies inside it.

He could then pay any sum of money from $1$p to $15$p without opening any bag.

How many pennies did Ram put in each bag?

This problem is based on Money Bags from 'Mathematical Challenges for Able Pupils Key Stages 1 and 2', published by DfES. You can download a copy here.