Estimating Sums and Differences•Rounding•Clustering•Front-end-estimating

RoundingMost of the time, you will be asked to round to the nearest whole number.Round to the ones place, and drop the decimal part of your number.

Example: Estimate the sum of 10.93 and 3.25.

10.93+ 3.25

1111.003.00 3

14

ClusteringUse when all numbers are close to the same amountIf so, round each number to the same number.Then multiply

Ex) $2.44 + $1.86 + $2.11 + $1.70

$2 x 4 = $8

Front End EstimationAdd or subtract the values of the digits in the front place or left-most place value.

Usually gives a sum that is less than the actual sum.

Example5.45

9.89

3.53

6.03+

Front-end: 5 + 9 + 3 + 6 = 23

About 23