Identify the target digit to which you will round. For example, if the problem asks you to round to the tens place, you will identify the digit in the tens place for each factor in the calculation. To help identify the target digit, you may wish to underline it in each factor.
Look at the digit directly to the right of the target digit. If the digit to the right of the target digit is 5 or more, you will increase the target digit by one. If the digit to the right of the target digit is less than 5, the target digit will remain the same.
Replace all digits to the right of the target digit with zero. Be certain that the new rounded number has the same number of digits to the left of the decimal place as the original number. If you are rounding a decimal, the digits to the right of the target digit may be eliminated.
Calculate the problem using the rounded numbers. The calculation will likely be made easier through the use of rounded numbers. However, your result will be an estimate of the true answer to the original problem.