How to Use a Calculator to Find Ratios

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Ratios describe the relationship between two similar values, showing the number of times one value contains or is contained within the other. For example, the ratio of female students to male students is 4 to 1 means there are four female students for every one male student. It's easy to find ratios on a calculator.

    Identify the two points of data. For example, say you want to find the ratio of strawberries to raspberries in a garden that has 108 strawberries and 84 raspberries. Your points of data are 108 and 84.

    Determine the greatest common factor for both numbers in your ratio. This is the largest number that can be divided into both numbers equally. In this example, the greatest common factor is 12 because this is the largest number that divides both values evenly.

    Enter your first number into the calculator. In this example, enter the total number of strawberries, 108.

    Press the divide (÷) button on your calculator then enter the greatest common factor, which you found in Step 2. Hit the equals (=) button. Write this number down. In this example, you work out 108 ÷ 12 = 9.

    Enter the second number in your ratio. In this example, enter 84.

    Press the divide button, enter the greatest common factor and press the equals button. Write this number down. In this example, you work out 84 ÷ 12 = 7.

    Express your ratio using the number in Step 3 and the number in Step 5. In this example, the ratio is 9:7. In other words, the ratio of strawberries to raspberries is 9:7. For every nine strawberries, there are seven raspberries.

    Tips

    • You can express ratio in different ways. In this example, you can express the ratio as 9:7, 9 to 7 or 9/7.

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