Work Step by Step
When we use front-end estimation, we first add or subtract all of the first digits of each number. Next, we round the rest of the digits and then add or subtract them. Finally, we add the two components (the first digits and the other digits) to get the answer. Remember, we round any digit from 5 to 9 up and any digit from 1 to 4 down. Thus, we find the sum of the first digits: 1+2+7=10. Now, we find the sum of the other digits, which are estimated: .4+.4+.7=1.5. We add the two components to get an answer: 10+1.5=11.5.