It can be useful to **estimate** the answer to a question.

We often do this to see if the actual answer is likely to be correct - the estimation should be quite close to the answer!

We can use **rounding **to help us make a good estimation of an answer.

Some numbers need to be **rounded up** and others need to be **rounded down.**

In this activity, we are going to use our knowledge of the number system to make** estimations rounding to a multiple of 5 or 10.**

Have a look at the following example.

**Example 1**

**652 + 326 **

We can see that **652 **is close to **650**

We can see that **326** is close to **325**

These numbers are quite simple to add mentally (or on paper if we need to).

**650** + **325** = **975**

The actual answer is **978 **(975 was a really good estimate).

We can check our answers using the inverse operation: 978 - 326 = 652

**Example 2**

**83 - 31**

We can see that **83**** **is close to **80**

We can see that **31** is close to **30**

Now subtract: **80 - 30 = 50**

The actual answer is **83 - 31 = 52** (another good estimate).

Rounding the number to the nearest multiple of 5, 10 or even 100 can help us make a good estimate.

We can check our answers using the** inverse operation**: 52 + 31 = 83

Are you ready to try some questions now?