What Is the Difference Between Rounding & Estimating?

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Rounding and estimating are math strategies used for approximating a number. To estimate means to make a rough guess or calculation. To round means to simplify a known number by scaling it slightly up or down. Rounding is a type of estimating. Both methods can help you make educated approximations and can be used in everyday life for tasks related to money, time or distance.

How to Round Numbers

Rounding means decreasing the amount of digits in a number but keeping the number close to its original value. To round a number, decide on the digit you want to round to. Look at the digit to the right of that rounding digit. If the number is 5 or greater, bump the rounding digit up one number. If it is less than 5, drop it down one number. In a decimal, remove all of the digits after the rounding digit. For example, if you want to round 7.38 to the nearest 10th, the answer would be 7.4. In a whole number, change all digits to the right of the rounding digit to zeros. If you want to round 62 to the nearest 10, for instance, the answer would be 60.

How to Estimate

Estimating is different than rounding because it is a broader form of approximation. Estimation is used when coming up with a brand-new number instead of modifying an existing one. For example, a person might estimate how long it would take him to mow the lawn, how far it is to a friend's house or how many feet of carpet are needed to cover the floor of a particular room. Estimations are based on prior knowledge and given information. They are not exact measurements. If your usual jogging pace is between a nine- and 11-minute mile, for example, and the supermarket is two miles away, you might estimate that it would take you roughly 20 minutes to jog to the supermarket.

References

About the Author

Rachel Pancare taught elementary school for seven years before moving into the K-12 publishing industry. Pancare holds a Master of Science in childhood education from Bank Street College and a Bachelor of Arts in English from Skidmore College.

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