When we are working with very large numbers or with decimal numbers that have many places after the comma, there is a high chance that we will make a mistake in our calculations. An alternative is to use the rounding process to make numbers more accessible. See two situations:
1°) Rounding of Integers
When a number contains a large number of digits, we can round it to make calculations easier. See how a number is sorted into orders and classes:
Recall how a number is classified into orders and classes
Each column represents an order. Units are 1st order, tens the 2nd order; the hundreds, the 3rd order; units of thousands, the 4th order; and so on.
For example, if the area of a country is approximately 4.532.789 square kilometers and we want to do any calculation using this number, we can approximate it, that is, we can, for example, round it to the nearest thousand unit. This tells us that the numbers that are to the right of the thousand unit will be replaced by zero and we will keep the number 4.532.000. If we want to round our value to the nearest ten thousand, we will replace by zero all the digits that are to the right of the tens of thousands and we will keep 4.530.000. Following this reasoning, we can make numerous types of approximations. When we do this type of rounding, the final result of our calculation will not be exact, it will be just a I estimated. But this estimate brings us very close to the actual result. Remember that the more rounding we do, that is, the more digits we replace by zero, more imprecise will be our result.
2°) Rounding of Rational Numbers (Decimals)
When working with decimal numbers, we can come across numerous decimal places, which can also make calculations with these numbers difficult. We must initially choose how many decimal places we want to work with. Once that's done, we're going to analyze the first digit on the right that we want to remove. sand this number is 5, 6, 7, 8 or 9, we will increase by one the last digit we are working with. If none of the values described appear, our decimal number will remain intact, without the need to change it. Suppose we want to round the following numbers to just two decimal places:
1,5687 → 1,57
24,9876 → 24,99
159,369871289 → 159,37
75,36012 → 75,36
123,05325 → 123,05
By Amanda Gonçalves
Graduated in Mathematics
