How does estimating an addition or subtraction problem help you know if ananswer is reasonable?

When estimating an addition or subtraction problem, you can easily tell if it is reasonable or not. If you're having trouble with a problem, such as 1342+7864, and you're getting an answer of... 1300, but don't think its correct, you can estimate by rounding the numbers and adding them. For example, 1342=1300 and 7864=7900 (I'm using the rule that if the number is 4-0 I round down and if its 5-9 I round up.) Since we're woring with thousands you would try to get the most split, even value you can without taking off too much, so we would round the tens place. And after that you could add 1300+7900=9200. Then you would know your answer of 1300 is not reasonable and you have an error in your equation.  Estimating is a great skill to have, and it really helps when you're just trying an equation out or get one of those "Estimate the sum of" questions.

Hope this helps! I didn't copy it from anywhere, just wrote it myself :) Brainliest would be awesome!

the answer is 4.8 units on e2020.