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Maths I

Time calculations

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# Calculating time intervals

In the General exam you might be asked to work out how long someone spends at work during the day or how long a train journey lasts. This is calculating a time interval.

For most things we use the decimal system of counting, i.e. hundreds, tens and so on.

Time isn't counted like this because, instead of going up in tens:

• 60 seconds = 1 minute

• 60 minutes = 1 hour

Be careful! Lots of people make mistakes when doing time calculations because of this.

There are lots of different methods for calculating time intervals. It doesn't matter which one you choose, as long as you feel confident about using it. However, whichever way you decide to do these questions, show all your working, it helps to stop you getting confused between time and decimal systems of counting.

## Here is an example of a typical time question -

Daniel starts school at and finishes at . How long does his school day last?

We will go over two ways of doing this, using Time Lines and Counting On.

## Time Lines

This is where the time interval is shown on a time line.

First draw a line with (when Daniel started school) at one end and (when Daniel finished school) at the other.

Next mark and on the line.

If you want to, mark in noon.

Now calculate the time interval for each section.