IXL | Estimate sums and differences using compatible numbers

Use compatible numbers to estimate

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First, pick the better pair of compatible numbers.

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Now, use your choice to estimate the difference.

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is about

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Learn with an example

question

Use compatible numbers to estimate

–

First, pick the better pair of compatible numbers.

–

Now, use your choice to estimate the difference.

–

is about

key idea

Compatible numbers are good for estimating differences. They are close to the numbers you are given, and they are easy to subtract in your head.

solution

You want to estimate

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So, find compatible numbers that are close to 78 and 32.

80 is close to 78.

30 is close to 32.

80 and 30 are compatible numbers. They are easy to subtract in your head.

So,

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is a good way to estimate the difference.

Now, subtract the compatible numbers.

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So,

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is about

50.

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isn't as good of a way to estimate

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40 is too far from 32.

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D.2Estimate sums using compatible numbers

E.2Estimate differences using compatible numbers

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