How To Cross Multiply To Solve For X

This video is an example of how to simplify a fraction and then solve for X using cross multiplication. Thanks for watching!

[chaikaomoua]

It seems like every year there is a new idea to make math harder.

[josh]

I don’t like memorizing “tricks“ in math. I like the tricks, because they make math quick, but don’t memorize them. Learn them. Understand them. This works because you can make equivalent fractions with the same denominator and multiply both sides by the denominator to get rid of it. Example: x/10=1/5. Multiplying each fraction by the denominator of the other divided by itself gives an equivalent fraction(x/x=1), and you end up with 5x/50=10/50, and you can multiply out the denominator. I love tricks, but I despise the blind memorization of them, because what happens when you forget? You never learned an intuitive understanding, so you can’t just figure it out.

[josephcauthen]

Why did you multiply by 5 then immediately divide it back out?

[davidkingsley]

7 times ten is 70
35 goes into 70 two times
X = 2