Proportion

April 3,2009

Aim: how do we solve proportions by using cross products?

Today in class, we learned how to solve proportions using cross products. Cross multiply is a easier way to solve proportions because it make the work easier by organizing it for you. All you have to do is circle the numbers diagonally and multiply.


2 x
_ = __; 2x=36; x=18
3 12


There is many things wrong with this is that instead of cross multiplying, they went straight across. That is why this person received the answer of 18.


The way you find out if the ratio of 6:45 and 2:15 is first, you multiply 6 and 15. That becomes 90. Then, you multiply 2 and 45 which is 90. Both ratios are 90 so it is proportional.

For example, 12/15, x/20. First you have circle 12 and 20 and 15 and x. Then you multiply 12 and 20 and that be