Question

Why is estimation useful when finding actual products and solving real-world problems? ​

Answer 1

It's Cause We Study Real-World-Problems  Without Education We wouldn't learn anything so its good to study independently so our brains can grow!  

Answer 2

Estimation is useful to quickly compute a value without needing a calculator. This way you can get a sense of scale of a project. Of course, when it comes time to doing the actual project, you should compute more accurate values to avoid rounding error.

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For example:

2.3*5.7 estimates to 2*5 = 10

The actual value is 2.3*5.7 = 13.11; we see the estimate 10 is an underestimate. The estimate isn't too far off, so we get a sense of the size/scale of this product.