# Can you do 133 with 3 zeros

## Rough calculations

bettermarks »Math book» Numbers »Natural numbers» Adding and subtracting up to 1,000,000 »Rough calculations

### rough calculation

Sometimes you don't need the exact result, but you want to get an idea of ​​the result of a task. You can use a rough calculation to do this. This makes the calculation easier and you can easily do the math in your head. When doing a rough calculation, you first round all the numbers and then calculate with the rounded numbers.
estimate the result of. Round up to hundreds by rounding all the numbers to hundreds.Then add up the rounded numbers.
estimate the result of. Round here in the thousands.

### Rounding point at the rollover

The rough calculation depends on the digit to which you round the numbers.
The rollover has only zeros to the right of the hundreds. The numbers and have been rounded to the nearest hundred.The rollover has only zeros to the right of the thousand digit. The numbers and have been rounded to the nearest thousand.

### rollover to check and classify calculation results

With the help of a rough calculation, you can assign the results of arithmetic problems to an area without calculating the exact result. The size of the area depends on the rounding point and the number of summands. By rounding up to hundreds, you move away from the exact result for each summand by no more than 50. When adding or subtracting two numbers, the exact result is therefore maximally smaller or larger , as the rounded result. By rounding up to thousands, you move away from the exact result for each summand by a maximum of 500. When adding or subtracting two numbers, the exact result is at most less or greater than the rounded result. By rounding up to tens of thousands the exact result for each summand is at most 5000. When adding or subtracting two numbers, the exact result is at most smaller or larger than the rounded result, etc.
One of the two calculations is correct. check which result is correct.The two results differ by. A rough calculation, rounded to the nearest thousand, can therefore provide reliable information as to which of the two results must be wrong. Calculation: The correct result cannot be further than the estimated result. This is only met by. Hence, only this can be right.
Rounding to the ten thousand digit is not enough, there and. So round to the thousand digit: Now you can be sure that, because the exact result can be a maximum of 1000 away from the rounded figure and.
The result of is between and, because.