Why do this problem?
can be done when the group are occupied with making straight-line graphs of multiplication tables and similar material. It could just nudge certain learners into something new. If they do not know the triangular numbers they could be shown how to work them out first. Drawing the graphs on paper is most
satisfactory, although a graphing calculator or a computer can be used.
Is this a straight-line graph?
Which times tables have you done?
Do you know the figures you need for the triangular numbers?
What about the square numbers? How far do you think you will be able to get on that paper?
Learners could try sequences such as doubling or adding successively one, two, three. Alternatively this Matchsticks
problem could be used.
Some children might benefit from drawing the graphs of multiplication tables on paper. A graphing calculator or on a computer can also be used.