SUMMATIVE: Using Compatible Numbers to Estimate Subtraction

Front

What are compatible numbers?

Back

Compatible numbers are numbers that are easy to compute with mentally. They are often rounded numbers that make calculations simpler.

Front

How do you estimate subtraction using compatible numbers?

Back

To estimate subtraction using compatible numbers, round each number to the nearest ten or hundred that makes the subtraction easier to calculate.

Front

Estimate 611 - 396 using compatible numbers.

Back

610 - 400 = 210.

Front

Estimate 789 - 144 using compatible numbers.

Back

790 - 145 = 645.

Front

Estimate 77 - 28 using compatible numbers.

Back

80 - 30 = 50.

Front

Estimate 266 - 157 using compatible numbers.

Back

265 - 155 = 110.

Front

Estimate 109 - 75 using compatible numbers.

Back

110 - 75 = 35.

Front

What is the purpose of estimating in subtraction?

Back

The purpose of estimating in subtraction is to quickly find an approximate answer without doing the exact calculation.

Front

Why is it important to use compatible numbers?

Back

Using compatible numbers helps simplify calculations and makes it easier to check if an answer is reasonable.

Front

What is the closest compatible number to 396?

Back

The closest compatible number to 396 is 400.