How do i use cross multiplication to decide wheather a proportion is true or false?

3/4 = 15/16

5 answers

3 * 16 =?? 4 * 15
4 * 15= 60
3 * 16= 48

now what i do? how do i know if its true or fasle?
Does 60 = 48??
Oh okay.. the number has to be the same in order for it to be true. So this problem would be false
Right. By cross-multiplying, you've proved this proportion to be false.