Business Mathematics Brief 12th Edition by Stanley Salzman ,Gary Clendenen, Charles Miller

تمرين 271

It is a good idea to estimate an answer before actually solving a problem. Why is this true? (See Objective.)
Estimate answers. Check that the numbers in Example were correctly added by estimating the answer. Apply front-end rounding to the numbers as follows.

The answer is relatively close to the actual value found of 156.4902 giving confidence that the original decimal numbers were added correctly.
Another option is to round each of the numbers to the nearest whole number and then compare as follows.

The sum of 156.4902 is very close to the estimate of 157, so it appears the addition was done correctly.