Mrs Beeswax
Problem
Mrs Beeswax was making three traditional English plum puddings.
She had ten old golden coins and wanted to put at least two in each pudding.
How many ways could the ten coins be placed into three puddings so that each pudding ended up with at least two coins?
Getting Started
How will you know you have found all the different ways?
Student Solutions
We had ideas from the Inter School in Zurich, Moorfield Junior School, Higher Bebington Junior School on the Wirral, Yarm Primary School, Cummersdale School in Carlisle as well as from students in Etobicoke, Ontario, Canada. There was quite a range of answers for this problem, from four ways to $740$ ways to put the ten coins into the plum puddings!
Here's what Tom did. He was very systematic, so we know that he has counted all the possibilities and hasn't counted any twice.
I know that each pudding must have at least two coins.No pudding can have more than six coins, or there wouldn't be enough left for the other two.
If one pudding has six coins, then the other two must each have two coins, and that uses all ten.
If one pudding has five coins, then one of the others must have three and the other two.
If one pudding has four coins, then either another could have four and the third just two, or the remaining two could have three each.
If no pudding has four or more coins, then we wouldn't have used all the coins. So these four possibilities are the only ones.
Teachers' Resources
Why do this problem?
Possible approach
Key questions
How are you thinking about this?
Do you think you've found all the possible ways?