ELI5: Explain Like I'm 5

Arithmetic precision

Imagine you have a pile of 10 toys and you want to divide them equally between your two friends, Bob and Sue. You give Bob 5 toys and Sue 5 toys. This is a fair way of dividing the toys because each friend got the same number.

Now imagine you have a pile of 7 toys and you want to divide them equally between Bob and Sue. You can't give them each 3.5 toys because you can't divide a toy into fractions. So you have to round the number up or down. If you round down, Bob would get 3 toys and Sue would get 3 toys, but there would be one toy left over. If you round up, Bob would get 4 toys and Sue would get 3 toys. This is still not completely fair because Bob got one more toy than Sue.

Arithmetic precision is a similar concept in math. When we do calculations with numbers, there can be some numbers that can't be represented exactly. For example, 1/3 is a number that can't be represented exactly as a decimal. It goes on forever like 0.3333333333...

When we do calculations with these numbers, we have to round them off to a certain number of decimal places to get an answer. But depending on how we round them off, we may end up with an answer that is a little bit too big or too small.

This can be a problem in some situations where we need to be very precise. For example, if we are calculating the amount of medicine a patient needs, we need to be very careful that we don't give them too much or too little. Even a small difference in the amount could be dangerous.

So mathematicians have developed methods for dealing with arithmetic precision. One way is to use more digits in our calculations, so that we can get a more accurate answer. Another way is to use a rounding method that reduces the amount of error.

In summary, arithmetic precision is about working with numbers that can't be represented exactly, and finding ways to get answers that are as accurate as possible.