How to Solve a Rule of 3 Problem: Step-by-Step Proportion Method
Learn how to solve a rule of 3 problem using proportions with a simple example involving cost and quantity.
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To solve a rule of 3 problem, you set up a proportion. For example, if you know that 2 apples cost $4, and you want to find out how much 5 apples cost, you write: 2/4 = 5/x. Then, cross-multiply to get 2x = 20. Solve for x by dividing both sides by 2, giving you x = 10. The cost of 5 apples would be $10. This method helps you find unknown values based on a proportional relationship.
FAQs & Answers
- What is the rule of 3 in mathematics? The rule of 3 is a method to solve proportions by finding an unknown fourth value when three values are known, based on their proportional relationships.
- How do you set up a rule of 3 problem? You set up a proportion by equating two ratios, for example, a/b = c/x, where x is the unknown you want to find, then solve for x.
- Can the rule of 3 be applied to real-life problems? Yes, the rule of 3 is commonly used in real-life situations such as calculating costs, distances, and quantities when proportional relationships exist.