Estimate Sums and Differences

Sometimes an exact sum is needed. However, in some cases, only an approximate answer can solve our problem. We can estimate by finding an answer that is close to the exact answer

To estimate the sum of two numbers, round each number and add

When two numbers have different number of digits, it is best to round to the highest place of the smaller number

To round to the nearest dollar look at the ten cents. If ten cents value is 50 or greater than 50, we round to the next dollar. If ten cents value is less than 50, we round to that dollar

Sometimes an exact difference is needed. However, in some cases, only an approximate answer can solve our problem. We can estimate by finding an answer that is close to the exact answer

To estimate the difference of two numbers, round each number and subtract

When two numbers have different number of digits, it is best to round to the highest place of the smaller number

To round to the nearest dollar look at the ten cents. If ten cents value is 50 or greater than 50, we round to the next dollar. If ten cents value is less than 50, we round to that dollar

When the number to be rounded is 5 or greater than 5 it is always rounded up. When we round up we increase each number. So, their sum is greater than the actual sum

When the number to be rounded is less than 5 it is always rounded down. When we round down we decrease each number. So, their sum is smaller than the actual sum

To estimate the difference of two numbers, round each number and subtract/add

When two numbers have different number of digits, it is best to round to the highest place of the smaller number