Algebra
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Unit 2: Solving Equations
Lesson 2.7: What is a Proportion and How Can We Solve It?
A proportion is an equation that sets a ratio equal to another ratio.
We saw a few proportions in the last lesson. We can say that your heart beats 6 times in 5 seconds or 12 times in 10 seconds.
As long as you multiply (or divide) both numbers in a ratio by the same number, you will always end up with an equal ratio.
This works because we are multiplying by a version of 1, which is the Identity Property of Multiplication.
This works because we are multiplying by a version of 1, which is the Identity Property of Multiplication.
The real fun begins when we put unknowns into the proportion.
The simplest move to solve a proportion is called cross-multiplication. It's like a double multiplication move.
With enough practice, you'll be cross multiplying quickly and accurately.
The simplest move to solve a proportion is called cross-multiplication. It's like a double multiplication move.
With enough practice, you'll be cross multiplying quickly and accurately.
Cross Multiplication:
Classwork & Homework:
Scale Drawings and Similar Figures: