Rule of Three – calculate the Rule of Three on the iPhone

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Remember this equation?

Remember this equation?

Have you ever been in such a situation: You just bought 25 apples for $5.25 and want to know how much 3 apples are? You invited 9 people for dinner but your recipes are only for 4 people. How much of each ingredient do you need to use for 9 people?

Do you remember the Rule of Three? That little equation with three known variables that easily allows you to calculate the fourth unknown? With "Rule of Three", this is now possible on your iPhone or iPod touch!

And these are the rules: Enter two numbers in relation with each other. Enter the third variable and press the equal button. "Rule of Three" immediately calculates the fourth unknown variable. There's no need for mental math anymore. In the example with the apples above, you would enter this equation: 25/5.25 = 3/x. The result is $0.63.

Use your fingers to calculate the Rule of Three

Let "Rule of Three" help you!

"Rule of Three" can help you in everyday situations, e.g. when confronted with taxes or percent calculation. You can also calculate aspect ratios if you're scaling proportionally. While on a trip abroad, quickly convert between currencies.

"Rule of Three" is not a normal calculator, it's the easiest and quickest way to handle the Rule of Three!

Learn more about the Rule of Three on Wikipedia.

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