Why did you multiply 15 by 3?

I'm assuming that you want to know what we get when we multiply 15 by 3.
15  3 = 45.

If you are confused, then read on. :)

The  symbol means you add 15 exactly 3 times. 15+15+15=45.

Let's take  for example.  is when you add 3 for a total of 2 times. 3 + 3 = 6. You can also say that  is when you add 2 for a total of 3 times. 2 + 2 + 2 = 6.

So 15  3 = 45.
15 + 15 + 15 = 45
and
3 + 3 + 3 + 3 + 3 + 3 + 3  + 3 + 3 + 3 + 3 + 3 + 3 +3 +3 = 45.

So the answer is 45. :)