For each year that goes by, the distance from those old school days grows longer and longer. What you learned back then, keeps getting harder to remember, especially math. Because to be honest, tell me how many times have you used the Pythagoras theorem since you finished school?

However, good ‘ol school math can be an excellent way to keep that brain fresh and sharp – for it is wonderful for your health to exercise the mind regularly.

And it’s just as important as having a fit body, especially when you start getting older. In addition, it is always fun to overcome a challenge; it gets your blood pumping!

Wherever you look today, you can see tips on how to have a long and happy life. There are exercises here and special diets there. What you hardly see is tips on how to keep that brain of yours healthy.

There are, of course, plenty of different ways to keep the mind sharp, as long as you make a space for them in your routine.

The most common examples are perhaps crossword and sudoku, but more recently, one of the oldest types of puzzles has reappeared.

## Good ‘ol maths

On the internet, it has become a trend for people to challenge each other to see who can solve them faster, and it is not about super-difficult puzzles that only a genius can solve.

No, the puzzles are just plain old math problems, like the ones you had back in school, which, on the other hand, becomes quite difficult considering how much time has passed since then.

To solve them, one really has to try to remember the observation and reasoning methods teachers passed down to us back then.

## How many triangles?

Here comes the challenge. It’s not proper math, but I remember our geometry teacher gave us a similar problem back in school.

Below, there is a picture – and the question is: how many triangles are in it?

How many did you find? The answer will be below the next picture.

## There are a lot of triangles

It is important to think a little outside the box to figure this one out.

The correct answer is ** 13** triangles, that is,

*.*

**option C****First, there are nine small triangles, that’s the easiest part.**

**Then we have three larger triangles that are made up of four small ones.**

Finally, we have a large one that composed of all the other triangles.

**9 + 3 + 1 = 13**

Did you get the correct answer? Congratulations to you if that’s the case, you are really sharp!

**Now press that SHARE button and see if your friends can do this!**