Estimation is the process of finding a value that is quite close to the correct value, but is not likely to be exactly the correct value. We usually need to use some thought and/or a calculation to make a good estimate.

For example, Jasmin entered a jelly-bean guessing competition. Rather than make a random guess, she decided to perform an estimation. She counted the number of jellybeans on the top layer in the jar, and found that there were \(23\). She then counted the number of rows, which was \(6\) and multiplied the two numbers together to come up with her estimate of \(6 \times 23 = 138\). Jasmin's guess was the closest to the actual number of \(142\) jelly-beans in the jar, so she won the competition.