Sometimes in everyday life, it is appropriate to use estimation when talking about numbers.

We may want to calculate an approximate answer to a problem quickly, where we don't need an exact answer.

We can use** rounding** to help us estimate a solution.

Rounding makes the numbers easier to calculate with, and so can often be done mentally.

**Example:**

Last month, I spent £187.63 on groceries, £112.37 on transport, and £45.15 on entertainment.

Estimate how much I spent all together?

I can round £187.63 to £188, £112.37 to £112, and £45.15 to £45.

Now £188 + £112 + 45 = £345

I estimate that I spent £345 last month on the above.

Did you notice that we had decimal numbers in the problem above? We rounded each of them to the nearest **whole number**.

Let's do the same in the next problem.

**Example:**

A pizza has 8 slices, and I estimate that each person will eat 3.5 slices.

Estimate how many pizzas I will need for a pizza party for 15 people.

Digits 0 - 4 round down, and digits 5 - 9 round up, so 3.5 rounds up to 4.

4 x 15 = 60 slices.

60 ÷ 8 = 7.5 pizzas.

We'd better round that up to 8 pizzas since we can't make half a pizza!

Let's do some more estimation practice.