# Estimation

Estimation is both a common mathematical term and a practical skill for daily life. It refers to using calculations or even simple observations to come up with a numerical value that is close enough to an actual measured value to be useful. In everyday terms, it’s making a quick but educated guess.

Learning how to estimate with reasonable accuracy can help with more than just getting a good grade on that next math test. Mastering this skill can save time on breaking out calculators or worrying about remembering more complicated numbers or equations.

**No Need to Break Out the Calculator**

A group of four friends go out to eat. They receive remarkably excellent service and want to leave their waitress a good tip. The total bill comes out to $39.53. Nobody wants to break out a calculator after a satisfying meal, so instead, the group estimates how much each of them would have to pay to leave a 20% tip. They round the bill up to $40, which makes it easier to figure out that a 20% tip would be $8. Each of them leaves an additional $2 and everyone, including their wonderful waitress, leaves happy without having to break out pens and paper to determine exact numerical values.

**Don’t Get Swindled**

In the real world, money matters. The same techniques can be used to get a general estimate of how much things should cost so that consumers can be confident they are not being overcharged as well. A shopper in a grocery store might round up all of the prices for the items he or she is about to buy and add them together. The end result will be slightly higher than the actual exact price he or she should expect, but if the price on the cash register is even higher than the estimate, the shopper will know immediately that something is wrong.

**Most People Already Use Estimation Every Day**

Although money is super important in this society it doesn’t count for everything, and getting quick answers that are still close enough to be useful can come in handy when it comes to calculating time, distance, area, and more. Much of the time an estimated number will be expressed verbally as an Approximation. For example: one student turns and asks another how much longer they have ’til class ends. The second student is unlikely to respond “9 minutes and 36 seconds.” He or she will likely round the number up to 10. This number is approximate, not exact, but it is more useful in the context of communicating intervals of time.

**Practice, Practice, Practice**

Students and adults alike estimate time and distances when they make plans, give directions, and perform any number of other daily tasks. As with any other skill, the best way to get better and more accurate at estimating amounts and numbers is to practice. Students may want to try exercises like estimating the number of books on a library shelf. To do so, they could count how many books are on one shelf, then simply multiply the number of books by the number of shelves. The result will not reflect how many books there really are with mathematical accuracy, but that’s OK! Sometimes the answer doesn’t have to be exact.