Question

How many whole numbers are between 1 and 50 that are divisible by 2?

Answer 1

This question is ambiguous.
If you mean between 1 and 50 inclusive (including 1 and 50) the answer is 50/2 = 25
If you mean strictly between 1 and 50 (excluding 1 and 50) then the answer is 24
ie 2, 4, 6, 8, ... 44, 46, 48 and dividing each term by two we see 1, 2, 3, ... 22, 23, 24

To avoid this the question should specify “inclusive” or “exclusive”

Answer 2

25

Explanation:

The first number in the range 1 - 50 that is divisible by 2 is 2 itself. Then 4, 6, 8, ....

Here's one way to think and count:

`2 \rightarrow 1\\4 \rightarrow 2\\6 \rightarrow 3\\8 \rightarrow 4\\\vdots\\50\rightarrow 25`

In the table, the number on the right is half the number on the left. The numbers on the right are just counting numbers (natural numbers), so there are 25 even numbers between 1 and 50.