Transcript

INSTRUCTOR:

Here is a number line from 0 to 10. Let's put the part of the number line between 3 and 4 under an imaginary magnifying glass. Imagine I place a magnifying glass over the section of the number line between 3.1 and 3.2 showing 10 intervals. These numbers can be filled in. We will now magnify the line between 3.17 and 3.18.

As can be imagined, we could go on and look at four decimal place numbers. I hope you can see that as we use more decimal places, the quantities those digits represent are smaller and smaller. When we consider measuring in centimetres, we cannot measure much more accurately than to one decimal place-- possibly two decimal places. This gives some justification as to why we might wish to round many calculations using measurements to one or two decimal places.