For my Unit 1 Summary, I have decided to present how to cross-multiply fractions.
This concept seems complicated at first, but it is pretty easy to understand. You can use this concept whenever you are multiplying or dividing any number of fractions. This concept aims to make it easier to multiply complex fractions. Let’s use these two pairs of fractions as examples. (6/2 and 8/3) (24/7 and 28/32)
- The first step is to look at the first fraction’s numerator and the second’s denominator. (Or vice versa) Can they simplify together? If so, reduce them both. (6 becomes 2 and 3 becomes 1.)
- Then look at the next pair of numbers. (The first fraction’s denominator and the second’s numerator.) Then, reduce those. (2 becomes 1 and 8 becomes 4.)
- Then, multiply! (2/1 x 4/1 = 8.)
For the second pair of fractions, one number doesn’t have to be a prime number to cross multiply. You can reduce factorially.
- Same steps as before (24 and 32. can both be divided by 8, 24/8 = 3, 32/8 = 4.)
- Same steps. (7 and 28. Can both be divided by 7. 7/7 = 1, 28/7 = 4.)
- Multiply! (3/1 x 4/4 = 12/4 = 3)
COMMON MISTAKES (or at least mistakes I made.)
If you are multiplying more than 2 fractions, do the first pair first, and not all together.
Not just prime numbers can cross multiply. Multiples can too!
Thank you for reading.