2.3.2 Calculator Exploration: Decimals and Rounding
In the following exploration, you will learn how to work with decimals on the calculator, and you will revise rounding your answers.
The calculator can be accessed in the left-hand side bar
under Toolkit.
Calculations involving decimals are often more complicated than
calculations using just whole numbers, and this is when the calculator is
very useful. You enter the decimal point using the button marked 
. You’ll find this below the numbers on the calculator.
On your keyboard, use the period key.
| Mathematical Operation | Calculator Button | Keyboard Key |
|---|---|---|
| Decimal point | | Period key |
Now it’s time to try some calculations. Start with an easy one which you can do in your head:
The key sequence is:
Enter this on the calculator and check that you get the answer 3.8.
Activity: Working with Decimals
Use the calculator for these calculations.
(a)
Discussion
Remember to clear each calculation before you start
the next, using the 
button.
(b)
(c)
In the solution to part (c), you will have noticed that the calculator gave the answer in fraction format before converting it to a decimal. Don’t worry about this at the moment; it will be explained in Unit 7.
The calculator also displayed 14 decimal places in the answer. There are more digits after this, but 14 digits are more than enough for most purposes! In fact, 14 are usually too many, and so we round the answer to give a shorter, more useful form.
For example, if we were to round the displayed answer to 2 d.p., then we would look at the third decimal place, which is 8, to make our decision. Because 8 is larger than 5, it indicates that we would need to round up, giving us 3.27 as a rounded answer.
2.3.1 How Far is It?