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Competencies covered

MSFGN2001: Make measurements and calculations

Using a calculator

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If you're having trouble using a calculator, the best advice is to read the manufacturer's instructions.

Different calculators operate in different ways, and they don't always follow the same order for entering numbers and functions.

Here's a few general hints on how to use a calculator effectively.

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1. Clear the calculator before you start any new calculation.

This will ensure that nothing you did before gets mixed up with the calculation you are about to begin

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2. Write down the numbers first if they are complicated.

You should also write them down if someone is calling them out to you, such as while taking a series of measurements.

Then you can be sure that you're entering the right numbers, especially if they have decimal points or several zeros.

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3. Estimate the answer in your head if the numbers are long or complicated.

This will help you to pick up mistakes, because it will give you an idea of the size of the answer you're looking for.

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For example, if you had 18 carpet grippers that were each 1.2 metres long, and you wanted to know what the total metreage was, you could do the following calculation in your head:

20 (rounding up 18) x 1 (rounding down 1.2) = 20

So when you do the actual calculation and find that the answer is 21.6 metres, you'll know that it sounds about right.

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The rule of thumb for rounding off numbers is:

     Ending in a 5 or more - round up

     Ending in a 4 or less - round down

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Learning activity

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Here are some rounding exercises. Enter your answer in the cell beside each number or calculation. When you've finished each question, click on the 'Check your answers' button to see how you went.

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Round off these numbers ValueEnter the rounded value
to the nearest whole number6.3 6
to the nearest whole number5.2 5
to the nearest ten78 80
to the nearest ten14 10
to the nearest hundred85 100
to the nearest hundred530500

Estimate the answers to these calculations

You may either do these sums in your head, or use a calculator.
But remember to write down your estimated answer, not the actual answer.

CalculationEstimated value
42 x 68 2800
56 x 93 5400
28 x 3.9120
7.2 x 2.1 14