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Estimating a Quantity and Approximating a Result - Cycle 2
| Mathematics
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An approximation is a value close to a real value that is found by rounding or estimating.
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Rounding means giving a value close to a known number.
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Estimating means determining a value close to an unknown number.
In the following figure, we can see that there are lots of spiders.
Before counting them one by one, we can estimate how many we think there are. In this image, it looks like there are around 50 spiders. That’s our estimate.
Now, we count them one by one. We get a total of 56 spiders. This is the exact value.
We can then round this number to the nearest ten. So, we can say there are approximately 60 spiders in the picture. This is a rounded number.
The numbers 50 and 60 are two approximations of the exact number of spiders.
We can also estimate a measurement of length, area, volume, mass, time or temperature.
Here are a few examples:
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An ice cream cone is about 10 cm tall.
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You’re hungry and know that lunch will be ready soon, so it must be around noon.
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It’s warm enough that I can go outside in a bathing suit, so the temperature must be around 25°C.
We can also approximate the result of a calculation.
For example, to find the approximate result of a complex addition problem, we can round the numbers before adding them.
A music festival had 91 627 attendees on Day 1 and 47 945 attendees on Day 2. Approximately how many people went to the festival in total?
Before adding the two numbers, we’ll round them to the nearest ten thousand.
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91 627 is between 90 000 and 100 000, but closer to 90 000, so we know that 91 627 rounded to the nearest ten thousand is 90 000. |
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47 945 is between 40 000 and 50 000, but closer to 50 000, so we know that 47 945 rounded to the nearest ten thousand is 50 000. |
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91 627 + 47 945 |
Answer: In total, approximately 140 000 spectators attended the festival.