To help you get started on this very challenging problem, Alison made a series of videos showing some ways to work on this problem. Perhaps after watching each video you could have another go at solving the problem for yourself before looking to see what Alison does next.

In this video, Alison outlines the problem and starts thinking how to get started.

In this video, Alison multiplies and divides to try to get close to the solution.

In this video, Alison restates the problem in a different way.

In this video, Alison thinks about factors.

In this video, Alison finds a representation that helps.

In this video, Alison considers the units digit.

In the final video, Alison tries some more combinations and finds one that works!