## Rounding Whole Numbers

#### Introduction

Rounding is a useful tool in math, as it allows us to get a rough sense of a number to do quick mental math. For example, if you are hosting a party for 19 people, and you want to buy enough small cakes for everyone at the party (you assume 3 per person will be enough), you can round 19 guests to 20, which makes calculating the total number of small cakes much easier (since 20 x 3 is easier to work out than 19 x 3).

#### Terms

## Lesson

To round a whole number, you first have to decide how precise you need to be. If you only need a rough estimate, you can be very broad with your rounding. If you need a more detailed estimate, you need to be a bit more specific.

For example, if you are trying to work out what to budget to buy a new pair of shoes, it doesn't matter if you estimate a pair of shoes to be $50 or$100. If, however, you want to work out how much wallpaper to buy to decorate a room, the difference between 50 square yards and 100 square yards is too big.

In order to round a whole number, you need to turn it into a number with a zero at the end. If you need to be quite precise, then usually one zero will work. If you don't need to be precise, then you can round to a number that has a single digit followed by zeros.

For example, let's say you have money in a savings account totaling $468.00 There are two different levels of rounding you can do. If you want to be quite precise, but still round, you could say you have roughly$470. If you don't need to be precise, you can round to $500.

The key question with rounding is how precise you need to be. That will determine which 'landmark number' you need to get to.