This morning I asked my math class to find the areas of two right-angled triangles. Lottie-Lu's hand shot up immediately, so I asked her the first one.

"24" she announced.

She was right (for a change!) and I made the mistake of asking her how she did it.

"Easy. Just add all the sides together."

I was about to correct her and say it was just a coincidence, when I noticed that her method worked on my second triangle as well!

Lottie-Lu must have caught my frustrated thoughts. "Well, it works, doesn't it?" she chirped.

What were the side lengths of the two triangles I had drawn on the board this morning? They were all whole numbers.