We haven't had any maths for a while, so I thought it was time. Don't worry, this one's simple and involves money, something which I'm sure is dear to all our hearts.
Supposing you had some coins. Whilst you were thinking what to spend them on you might amuse yourself by arranging them into a geometrical shape. Such as the kind of triangular arrangement that you see on a pool or snooker table:
If the coins can be arranged like this, then we say that it is a triangle number. For example, 10 coins could be arranged in a triangle because 1 + 2 + 3 + 4 is 10. But 8, 9 or 11 coins couldn't be.
Having still not decided what to buy, you could arrange them into a square:
9 coins could be arranged in a 3 x 3 square, but if you tried with 10 coins, it wouldn't work.
Now supposing that you had one coin for every year you'd been alive, and that you were able to arrange them like I did into both a triangle and a square. Then you'd be exactly the same age as Bee, since only one number is both a triangle and a square. I'm sure Bee is neither.