We are sometimes encouraged to **estimate** answers (have a sensible guess).

Estimating gives us an answer that is close to the actual answer and can help us see if an answer is likely to be correct.

We can round to the nearest 10, 100, 1,000, 10,000 etc.

In this activity, we are going to practise rounding to the **nearest 10** to **estimate some addition** questions.

A two-digit number that ends in **five** or above **rounds up** to the next ten.

A two-digit number that ends in **four** or below **rounds down** to the previous ten.

**Example 1**

Estimate the answer to the following sum by **rounding** the numbers to the** nearest ten **and then **adding**.

**38 + 12**

**Answer**

3**8** rounds **up** to 40

1**2** rounds **down** to 10

40 + 10 = **50**

The actual answer is 50 - a great estimate!

**Example 2**

Estimate the answer to the following sum by **rounding** the numbers to the** nearest ten **and then **adding**.

**64 + 55**

**Answer**

6**4 **rounds **down** to 60

5**5** rounds **up** to 60

60 + 60 = **120**

The actual answer is 119 - another great estimate!

Remember, when **rounding down** we go back to the previous ten - 43 rounds down to 40 (not 30)

Let's have a go at some questions now - good luck!