Let’s Learn!

Think About It!

Goal: Round the addends of an addition sentence.

We can help Elise by adding 32 + 47. 32 and 47 are big numbers. They are hard to add together. Let’s try rounding them to the nearest 10 instead.

Rounded addends make an estimated sum. The sum is not exact, but it is easy to find.

Step 1:

Find the addends on a number line.

Step 2:

Round the addends. Which benchmark numbers are closest?

Step 3:

30 + 50 = 80

Add the rounded addends together.

Rounding changes a number to help us add. Adding rounded addends makes an estimated sum.

Let’s add 32 + 47. Look at the real sum and the estimated sum.

Show Me

Real Sum

Estimated Sum

The estimated sum is very close to the real sum. The rounded addends are whole tens. It is easier to find the estimated sum.

What is the estimated sum of 49 + 64? Use the number line below to help!

1. 40 + 60 = 100
2. 50 + 40 = 90
3. 50 + 60 = 110

Sorry, that is not correct. The estimated sum is 110.

Sorry, that is not correct. The estimated sum is 110.

Great job! The estimated sum is 110.

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