In this activity, we will be learning about using estimating in maths.

When we estimate, we do not carry out exact calculations.

We work things out using **approximate** values.

To do this, we might **round **a number up or down to the **closest multiple** of 10 or 100.

7 and 11 are both approximately **10**

48 and 51 are both approximately **50**.

389 and 403 are both approximatel**y 400.**

So, if there are 396 jelly beans in a jar and Simon has two jars. How many beans does he have altogether?

396 is very close to 400.

400 is much easier to **double** than 396.

400 × 2 = 800.

So, we could say he has **approximately 800** jelly beans.

Let's try an example question together.

__Example__

Benny's socks are 19 cm, 17 cm, 21 cm, and 22 cm long.

He lays them out in a line.

Approximately how long is the line?

**Answer**

Benny's socks are all approximately 20 cm long if we round them all to the nearest multiple of 10.

He has four pairs of socks.

20 × 4 = 80

The line of socks will be approximately 80 cm long.

Now you've seen estimating in action, it's time to try some questions yourself.