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.