6/16 OR 30/80 WHICH ONE is bigger?

There's two possible ways to find the answer to this.  First you can find a common denominator to reduce both to.  In this case, they can both reduce to a common denominator of 8.  So 6/16 reduces to 3/8 and 30/80 also reduces to 3/8, so they are equal.  The other way is to use a calculator and turn them into decimals by dividing the numerator by the denominator.  They both come out to be .375. Once again they are equal.  You can use whichever method is easier for you.

You have to change them to the same denominator (bottom). The quickest way to do this is to x them by each other.. 16 x 80 = 1280
Then x the top of each by what you x'd the bottom by to get the common denominator...
6 x 80 = 480
30 x 16 = 480
The fractions would now be 480/1280 and 480/1280. They are the same. 6/16 is an equivalent fraction to 30/80. Neither is bigger.
Hope this helps :)