Take a look at the multiplication square.
In the multiplication square below, the first eleven triangle numbers 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66 have been identified.
Can you see a pattern?
Can you predict the positions of the next triangle numbers?
Check to see if you’re right.
Can you explain why triangle numbers take up these positions in a multiplication square?
Age 11 to 14