3.9 Cross Multiplication

Cross multiplication is an incredibly useful component of your transposition toolkit, used in situations where the formula or equation is in the form

In fact, we have been sort of cross multiplying in the last section. How does it work?

Let’s first look at a numerical example.

If you multiply both the numerator AND the denominator of a fraction by the SAME number, you get an equivalent fraction; the two fractions look different but they are both worth the same.