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'Cat Food' printed from http://nrich.maths.org/
Sam sets up displays of 105 cans of cat food in his shop in
triangular stacks. He puts 14 on the bottom row, 13 on the next one
up, 12 on the next and so on... and finally one on top, a stack 14
layers high. How tall would this stack be? Would it be taller than
Felix buys 33 cans of cat food so Sam can't make a triangular stack
with 14 layers. He stacks all the remaining cans into two identical
triangular stacks with one can in the top layer, two in the second
layer and so on. How many rows does each stack have? What is the
smallest number of cans Felix could have bought leaving exactly the
right number for Sam to make two identical triangular stacks?
Tom buys 7 cans from a triangular stack with nine rows. Sam
re-stacks the remaining cans into two new triangular stacks with
different numbers of rows. How many rows do the two new stacks
Sam finds he can arrange 49 cans into 3 triangular stacks in two
different ways. What do you think Sam's solutions were? Are there
only two possibilities? Can you find another number which can be
split into 3 triangular numbers in more than one way?
Make up your own can stacking puzzle.