6.2.2 Mixed Numbers on the Calculator

Calculator symbol The calculator can be accessed on the left-hand side bar under the Toolkit.

Notebook symbolActivity: Adding and Subtracting Mixed Numbers

Try adding these mixed numbers on the calculator. Can you work out how to do this?

(a)

Hint symbol

Discussion

Enter each number as the integer (whole number) part plus the fraction part.

Solution symbol

Answer

(a) You can rewrite the sum as equation sequence sum with, 4 , summands one plus two plus five divided by 12 plus one divided by six equals sum with, 3 , summands three plus five divided by 12 plus two divided by 12 equals. You may find it easy to add the whole numbers, then add the fraction parts separately, and then combine the results. However,there is no need to reorder.

Let’s enter the same numbers in the calculator without rearranging. You should see the following:

A final word of warning—the calculator does not always give the answer as a fraction.

(b) Try adding one divided by six plus one divided by three on the calculator.

Solution symbol

Answer

(b) The calculator goes directly to the decimal form of the answer: .

But, remember from our earlier explorations that you can convert a decimal to a fraction by clicking on the equals sign or hitting Enter. Try this, and you should find that the calculator changes 0.5 back into a fraction:

Here are another few examples to make sure that adding and subtracting fractions works for you.

(c) sum with, 3 , summands three divided by 24 plus five divided by six plus two divided by three

Hint symbol

Discussion

Give your answer as a mixed number.

Solution symbol

Answer

(c) The calculator goes straight to the decimal form:

Click on the equals sign to convert back to a fraction.

To check the calculation without a calculator, write all the fractions as twenty-fourths, because this is the smallest number that 24, 6 and 3 all divide into. This gives 39 divided by 24, which can be reduced to 13 divided by eight.

equation sequence sum with, 3 , summands three divided by 24 plus five divided by six plus two divided by three equals sum with, 3 , summands three divided by 24 plus 20 divided by 24 plus 16 divided by 24 equals 39 divided by 24 equals 13 divided by eight equals

(d)

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Discussion

Think hard about how you enter the second mixed number, ; remember that you want to subtract all of , that is both the 3 and the one divided by two.

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Answer

(b) When you enter the second mixed number, you need to subtract both parts. One way to do this is to put parentheses around the open three plus one divided by two close, to show that you are subtracting both parts.

The key sequence to achieve this would be:

The calculator shows:

Notice that the calculator has interpreted your entry as “subtract 3 and also subtract one-half.” This gives another way of entering the calculation.

You can choose the method that makes most sense to you but think carefully about what you subtract.

To recap:

  • To add or subtract fractions, enter them straight into the calculator and click the equals sign or Enter.
  • If there is not sufficient space to show the decimal number in the top screen, you will find more decimal places displayed in the white window below.
  • Take care when you subtract mixed numbers to make sure that you subtract both the whole number and the fraction part.

6.2.1 Adding and Subtracting Fractions with the Calculator

6.2.3 Adding and Subtracting Fractions