IXL | Estimate sums using compatible numbers

Use compatible numbers to estimate

139

First, pick the better pair of compatible numbers.

140

Now, use your choice to estimate the sum.

139

is about

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Learn with an example

Use compatible numbers to estimate

First, pick the better pair of compatible numbers.

Now, use your choice to estimate the sum.

is about

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

You want to estimate

So, find compatible numbers that are close to 43 and 19.

45 is close to 43.

20 is close to 19.

45 and 20 are compatible numbers. They are easy to add in your head.

So,

is a good way to estimate the sum.

Now, add the compatible numbers.

So,

is about

65.

isn't as good of a way to estimate

50 is too far from 43.

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