It shows the division ways by doing /
Yes; his answer is correct.
John can do this by multiple ways, but most likely he just remembered this one. Here are some ways.
1. He used his fingers; he put 1 finger, then another finger, and got 2 fingers up. The answer is 2.
2. He remembered it; usually Kindergarteners learn this and this is very easy to remember.
3. He used the things around him; I have 1 crayon then add another, how many do I have? 2.
We call:

as the set of <span>the first 51 consecutive odd positive integers, so:
</span>

Where:





<span>and so on.
In mathematics, a sequence of numbers, such that the difference between two consecutive terms is constant, is called Arithmetic Progression, so:
3-1 = 2
5-3 = 2
7-5 = 2
9-7 = 2 and so on.
Then, the common difference is 2, thus:
</span>

<span>
Then:
</span>

<span>
So, we need to find the sum of the members of the finite series, which is called arithmetic series:
There is a formula for arithmetic series, namely:
</span>

<span>
Therefore, we need to find:
</span>
Given that

, then:

Thus:

Lastly:
$3.75 would be rounded up and changed to $4
He maybe accidently added both of thm .
But if we difference we get 7.
Because - and - =+
So
-11+4=7.