In my estimation...1510

Estimation is not always for jelly beans guessing contests. No, no. Estimation is an important skill to have when doing addition, subtraction, multiplication and division. There are many strategies to help students estimate. Why do this? It can be a useful first step in order to get us on the right track as well as check our final answer.

What is important in estimation is knowing what you want to estimate...amount,lentgth, volume, an answer to a multiplication problem...once you know what you're looking for you can employ one of many strategies to determine your estimated answer.

Let us begin with answers to multiplication or addition problems...a superior strategy is rounding. If you are given a set of funky numbers to add or multiply you can use rounding to make them more friendly. So, say you've been given 23, 31, 19 and 15 to add. They are snarly numbers that don't add real nice at first glance. So you round them to the nearest 10...like 23 is nearest to 20 and 31 is nearest to 30. Those were easy but what about that mean looking 15? The general rule is to round UP. If we use that rule then the 15 would be thought of as 20. The 19 is snuggled right up next to 20 so that would also be 20 and we could then easily add 20+30+ 20+ 20 which equals 90.

In some cases, the estimated answer is good enough- like when you're at a big box store and throwing items willy-nilly in your cart and you have 100 bucks in cash and need to estimate if you have exceeded your wallet's capacity. If those numbers were prices I'd be able to stop because I'd know that I had enough money but I'd better high-tail it to the check out because one more clearance bargain might push me over the edge.

If they were numbers that represented diamonds, rubies, emeralds and opals, I'd want to know exactly how many precious gems I had in my possession. So I'd check it with my calculator and see that all told I had 88 gems and if I lend them to the Queen of England, I'd better get all 88 back.



So say you want to estimate the number of donuts to bring into work each day for a week and you remember than the last time that donuts were brought in there were 34, 27, 29,36 and 31 donuts consumed. You could use the clustering technique to estimate how many you should bring- all those numbers sort of cluster around a number...which looks like 30 to me. And since the donuts were brought in for five days you could multiply 30 times 5 and determine that bringing in 150 donuts will probably see you through.

Estimation, as I said, is not just for jelly bean guessing games, it is for donuts too.