If the number before the decimal place you want to round is greater than or equal to 5, we must increase 1 to the decimal point you choose for rounding. If the number is less than 5, just take the decimal places that don't interest us, and the number doesn't change.

Ex: 27.8 + 1,324 + 0.66 = 29,784

In this case, if we just want **an **decimal place after the comma, we must write 29.8. But if we want **two** After the comma, we should write 29.78.

We can also do the rounding **before** to perform the operation:

Ex: 27.8 + 1.3 + 0.7 = 29.8

**Attention:** *When you round before the operation, it may happen that the last digit is different from what you would find if you rounded after the operation.*.

**Another example: **

The length of a wire is worth 14269513 mm or is on the order of 1.43x10^{7} mm Note that we only use two digits after the comma with the last one being rounded up since 1.4269 is closer to 1.43 than 1.42.

Also note that by rounding the decimal places we lose much of the initial information, but this can be solved by using as many digits as needed after the comma, such as 1.4269513 x 10^{7} mm reproduces the value with all initial precision.