Estimate Sums & Differences

Front

What is estimating sums?

Back

Estimating sums involves rounding numbers to make them easier to add, allowing for a quick approximation of the total.

Front

How do you round to the nearest hundred?

Back

To round to the nearest hundred, look at the tens digit. If it's 5 or more, round up; if it's 4 or less, round down.

Front

Estimate the sum of 327 + 431 by rounding to the nearest hundreds.

Back

700

Front

Estimate the difference of 470 - 289 by rounding to the nearest hundreds.

Back

200

Front

What are compatible numbers?

Back

Compatible numbers are numbers that are easy to compute mentally, often used for estimation.

Front

Use compatible numbers to estimate 76 + 26.

Back

75 + 25 = 100.

Front

If there were 926 people at a tournament and 607 left, how do you estimate how many stayed?

Back

Estimate by subtracting 600 from 900, which gives approximately 300.

Front

Estimate the sum of 120 + 190 by rounding to the nearest hundreds.

Back

300

Front

What is the purpose of estimating in math?

Back

Estimating helps to quickly assess the reasonableness of an answer without calculating the exact value.

Front

How can you check if your estimate is reasonable?

Back

Compare your estimate to the actual numbers involved and see if it falls within a logical range.