# Rounding and estimating

This lesson about rounding and estimating will introduce you to some of the most common methods of estimation and rounding numbers.

In many cases, some calculations may require an exact answer instead of an estimation. Pretend that you buy some groceries from the supermarket.

You give the cashier 20 dollars for a purchase of 16.87 dollars. An exact answer is important here so you get back the change that you deserve. You definitely do not want the cashier to estimate the money you get back.

However, for other situations an estimate is sufficient unless you really want to be picky about it.

For example, suppose you lost a certain amount of pounds over the course of a year, you could be satisfied with an estimate. See below a list of the pounds you may have lost.

2.4, 2.5, 2.6, 2.3, 2.45, 2.60, 2.41, 2.35, 2.56, 2.49

Cluster estimation may help you see that you lost approximately 2.5 × 10 pounds or 25 pounds.

This unit has a lesson about cluster estimation, so read it so you understand how we used cluster estimation to solve the problem above about losing pounds. Rounding whole numbers
Learning to round whole numbers is fundamental. This is where all your studies start.Make sure you got a good understanding of this lesson before learning anything else. Take your time. We are not in a race here!

Estimating a sum
After you have mastered the lesson about rounding whole numbers, your next stop is right here. This lesson will show you how you can round to the nearest ten, or hundred to get the best estimate when trying to estimate a sum.

Front end estimation
Next, front end estimation is explored, which can be used to estimate product and division. Unlike estimating a sum, which may try to estimate by rounding to different places, front end estimation only round and add the numbers in the leftmost place. You must explore this type of estimating numbers!

Compatible numbers
Finally, compatible numbers will take estimation to a whole new level. If you have no clue what compatible numbers are, this is the time to learn what they are and how they are used to get good estimate for multiplication and division.

Cluster estimation
Learn how to use cluster estimation to estimate sums and products.

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