Barbara is tiling her craft room floor with square tiles. She wants 6/10 of squares tiles to be red. If she uses 18 red tiles, how many square tiles will be used to cover the floor?

6 and 18 are common because 6x3=18. Remember the rule to multiply all numbers by 3. So multiply 10 by 3 and you will get 30. The total number of square tiles needed is 30 tiles. If you are putting it into a ratio it would be 18:30.