Estimating Sums

Let's say you have$100.You go to the store to buy some toys. You check out their prices. Then, you add them in your head. But there's just too many numbers to add.

Do you know what can be useful at times like this?

Estimating sums!

**Estimating a sum** means to **make a guess **that's close enough to the true sum.

An estimated sum is **not the exact sum**, but it is very close to it.Β

Let's try to estimate the sum for:

52 + 39β?

π Note: When we estimate sums, we don't use the "=" sign. We use the "β" instead. We read this sign as "about."

Now, let's get to the steps in estimating sums:

**(1) First,** you **round the addends**.

π€ **Remember:** **addends **are the two parts you add together to get a whole.

In our problem, the **addends **are 2-digit numbers (52 and 39).Β

What is the highest place for 2-digit numbers?

That's right! It's the Tens place.Β

π So let's **round **each addend to the **Tens **place.

52 + 39 β 50 + 40 = ?

**(2) Then,** **add the rounded numbers**.

50 + 40 = 90

Now, we know that 52 + 39 β 90.Β

Or we can say **the sum of 52 + 39 is ****about 90**.

**Tip:** round to the **highest place value**.

π So if you're adding 2-digit numbers, round both to the **Tens.**Β

πΊ If you're adding **3-digit **numbers, round both to the **Hundreds!**

Let's try an example with 3-digit numbers.

286 + 542 β ?

**(1) First,** we round off each addend to the Hundreds.

286 + 542 β 300 + 500 = ?

**(2) Then,** we add the rounded numbers.

300 + 500 = 800

So, **the sum of 282 + 542 is ****about 800**.

You've got it! Now, you know how to use rounding to estimate sums.

Great job! π

Now, you can move on to practice. πͺ

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