The number half of 25 is 12.5.
We can break 25 up into two numbers, 20 and 5 (since 25 = 20 + 5). Half of 20 is 10, and half of 5 is 2 1/2. Adding these two parts together, we find that half of 25 is 10 + 2 1/2 = 12 1/2
