Why do 1.5 and 2.5 round to 2?

When we talk about rounding numbers, the general rule is to round up if the decimal is 5 or higher. However, when it comes to numbers like 1.5 and 2.5, we round down instead of up.

This is because in mathematics, we use a concept called “rounding to the nearest even number” or “bankers’ rounding” which helps to reduce a bias when rounding numbers. For example, if we round 1.5 to 2 and 2.5 to 2, it evens out the bias that would occur if we always rounded up.

By consistently rounding numbers like 1.5 and 2.5 down to the nearest even number, we maintain a more balanced result overall. This method is especially important in situations where small errors in rounding can compound over time.

So, the next time you see a number like 1.5 or 2.5 rounding to 2, remember that it’s all part of the mathematical principle of rounding to the nearest even number.