Algebra: Chapter 3-9 (p 148)
Proportion
A ratio of 2 quantities is a comparison, often expressed as a fraction. An equation that states that 2 ratios are equal is called a proportion. I prefer to just criss-cross, or cross multiply proportional problems, but the book’s way is OK too.
For example, `x/63 = 2/9`, I solve by criss-crossing. That becomes `x*9 = 2*63` or `9x=63*2` or `9x=126` and dividing both sides by 9 to clear the x, gives us `x=14`.
Here is a link from purplemath.com that has some more examples.
Intro to Algebra: 2-7 (p 89)
See yesterday’s writeup and purplemath.com link!