15= 3*5
14= 2*7
LCM(15,14)= 2*3*5*7= 210
15 and 14 go into 210 evenly~
A ratio is a numerical comparison between 2 similar objects, persons, figures, or ideas. For example if I have 5 cards and you have 10, I can say that you have twice as many cards as I do. Or take my 5 cards and multiply by 2 to get your 10. Another way I can say it is that the ratio between your cards to my cards is 2 to 1 or 2:1 (both mean the same thing). Let's say now I have x cards, but knowing that I have a 2:1 ratio from your cards to mine, I can say that you have 2x cards. There is alot more I can say, but this should get you started. Feel free to ask any following questions.
