Torez has 4 apples, Martin takes quarter of them and gives Torez one back. How many apples does Torez have after that?

Hello!

First, let's find how much apples is a quarter (one-fourth) of `4` apples.

It is evident that  `4 = 1+1+1+1,`  i.e. `4` is the sum of `4` equal parts, each of them is one. So by the definition of a one-fourth part a quarter of `4` is `1.`

Second, Martin takes quarter of `4` apples, i.e. `1` apple. The remaining quantity after this is `4-1=3.` Then he gives one apple back, so the quantity becomes `3+1=4`.

And this is the answer: after these manipulations Torez has 4 apples again.