Have you ever entered a jelly bean guessing competition? If you haven't, the idea is to guess the number of jelly beans in a jar. Each person writes down their guess, and the person with the guess that's closest to the number of jelly beans in the jar wins the jar of jelly beans. If you could get very good at estimating things, you would have a real advantage in a jelly bean guessing competition!

Estimation doesn't just help you out in competitions. It can help you in many other ways as well. For example, estimation can help you to work out:

• if a bill is correct.
• how far something is away, how big something is, how heavy something is or the angle between things.
• how much your grocery bill is likely to be.

If you learn to estimate, you might be able to get a good idea of how many flowers will fit in a flower bed, how many people will fit in a room, or how many people are at a cricket match.

Estimation doesn't give you exact answers, but it does give you answers that are close enough to help you make decisions.

Gus the snail is working on his garden again. He has decided to plant a new cabbage garden that measures 63 centimetres by 49 centimetres. He is at the garden centre, hoping to buy some new punnets of cabbage plants. Each punnet contains \(10\) plants, and cabbages have to be planted \(12\) centimetres away from other cabbages. Gus needs to work out how many punnets of cabbages to buy.

We can use estimates to help Gus out. Each row is about \(60\) centimetres long, so Gus will be able to plant about \(5\) cabbages in each row (\(12 \times 5 = 60\)). The garden is about \(48 = 4 \times 12\) centimetres wide, so Gus can plant \(4\) rows of cabbages. All together, Gus can plant about \(5 \times 4 = 20\) cabbages, so he needs to buy \(2\) punnets of cabbages.

You might be thinking that you have a calculator or computer, so you don't need to worry about learning to estimate. But the fact is, you still do! Sometimes you might press the wrong buttons on your calculator, or the calculator or computer might simply make a mistake because of a programming error. Learning to estimate will help you to catch those errors quickly. You'll know what sort of answer to expect, and will be able to catch it quickly when something is wrong.

For example, today I used the calculator on my phone to add up the numbers \(1,2,3,4,5,6\) and \(7\). It gave me the answer of \(88\). I knew, immediately, (because I was able to estimate) that this answer was wrong. The correct answer is actually \(28\), which is quite a bit less than \(88\). It's always a good idea to use your brain to double check everything.

We can use estimation for things other than the results of calculations. For example, the picture shows someone holding some grapes in their hand to estimate their weight. You might use your thumb, your hand or paces to estimate the length of something. Scouts learn to use sticks to estimate how far something is away from them. There are lots of different estimation techniques that can help you out in different situations.