By default, graphing and scientific calculators display fractions as decimals. So if you enter a simple fraction, such as 1/2, the display reads 0.5. Some scientific calculators offer a feature that allows you to display fractions without making the conversion. Using this feature, you can enter a complex fraction and simplify it right on your calculator. Calculators with this feature also allow you to receive a mixed number – or you can convert it manually. If your calculator doesn't have this feature, you can use a mathematical trick to manipulate fractions.
The Fraction Button
Calculators that display fractions sometimes have a special mode, called Math mode, that you must first select before you can enter fractions. When the calculator is in Math mode, the word "math" appears at the top of the screen. Once you have selected this mode (if necessary), look for a button with two boxes, one black and one white, arranged on top of each other with a horizontal line between them. This is the fraction button. On some models, the button may show x/y or a b/c. Pressing this button enables the fraction feature.
Once you have enabled math mode, you can more easily use improper fractions, execute subtraction and addition with fractions, and other operations like exponents or square roots can be visually displayed with fractions.
Calculators with the ability to display fractions have a special fraction key. Press this before entering the numerator and denominator of the fraction you want to enter. On TI-83 Plus and TI-84 Plus graphing calculators the fraction operator can be found by pressing the math button and selecting the first option.
Entering a Fraction
When you press the fraction button, a fraction template appears in the display. It sometimes consists of two blank boxes arranged one over the other and separated by a horizontal line. The cursor will appear in the top box. You can now enter the numerator of the fraction.
On some models, fractions appear as numbers separated by an inverted "L." This character represents the horizontal line that separates the numerator and denominator.
Press the cursor down key (the key with the arrow that points downward) to move the cursor from the top box in the display to the bottom if you calculator has number boxes. You can now enter the denominator. If you need to change the numerator, you can always return to the top box by pressing the cursor up key.
If you have the type of calculator that shows fractions in a single line, simply enter the denominator. There's no need to move the cursor.
If you want to enter a mixed fraction, press the shift key before pressing the fraction key. The display will show a third box to the left of the two fraction boxes, and the cursor will be in that box. Enter the integer part of the number, then press the cursor right key to move the cursor to the numerator box of the fraction.
On calculators with linear displays, enter the three numbers in this order: integer, numerator, denominator.
Handling Fractions on Calculators Without the Fraction Key
Although you can't display non-decimal fractions on a calculator without a fraction function, you can still enter them. First enter the numerator of the fraction, then press the division key and enter the denominator. Hit the "equals" key and the fraction will display as a decimal.
If you can't convert decimals to a fraction directly on the calculator, but the calculator can help you do it with a pencil and paper. Suppose you want to express 0.7143 as a fraction. You could write it as 7143/10,000, but maybe you want to reduce this to something a lot more simple, such as a denominator that's a single digit. To do this, enter the original figure as decimal number, and then multiply by the desired denominator. This gives you the numerator of the fraction. For example, if you want a fraction with 7 in the denominator, multiply 0.7143 by 7. The calculator will display the numerator, which in this case is 5.0001, which is close enough to a whole number of 5 to be equal. You can then write the fraction 5/7 on a piece of paper.
This conversion from decimal form to fractional form isn’t perfect, but it can provide an approximation of certain values without a fraction calculator. This type of conversion can often lead to a loss of accuracy, but we can decide how many decimal places of accuracy to maintain.
There are also many apps and websites that can help to handle fractions, decimals, and more complicated operations. Desmos is a very powerful (and free) online calculator that can directly convert from decimals to fractions. Excel and google sheets are also extremely powerful tools that can be used to find fractions. Additionally these resources can display figures in scientific notation and even calculate more complicated figures – like standard deviation. These tools can be used to solve fractions and much more!
About the Author
Chris Deziel holds a Bachelor's degree in physics and a Master's degree in Humanities, He has taught science, math and English at the university level, both in his native Canada and in Japan. He began writing online in 2010, offering information in scientific, cultural and practical topics. His writing covers science, math and home improvement and design, as well as religion and the oriental healing arts.