What is a Ratio?

Today in Math we learned about ratios. A ratio is a set of numbers that compare something to something else (see figure1). It can compare anything, fruits to Veggies, lemons to limes, or adults to kids.



There are 4 different ways to write a ratio. You can write it
- as is in figure 1, with a colon,
- as a fraction,
- as you would say it, or
- as a decimal (see figure 2).



Last, in order to do a math question with ratios, it must be done a certain way. i.e. if you were to do a question that asked “Find the unit price if 3 tickets cost $5.00. Do this using ratios.” you would have to set it up in a certain way. First, you write down what Professor Einstein has written in green (seen in figure 3). This is the base of the question. In both fractions, you must have the money amount on the top, and the amount of tickets on the bottom. Because we don’t know the amount of money that one ticket costs, we will put an “X” for that value. Next, in blue, we have to cross multiply. $5.00 x 1= 5.00, that is going to equal the other cross product which is 3X (seen in blue). In brown, we now see that he has divided both numbers by 3 in order to get the 3 on the right hand side out of the way (if you had something like 2X, 6X, or any other number and then X, you would divide by that number).


As you can see, Prof. Einstein has done the math for 5.00 ÷3 and has come out with 1.6 repeating=X. Except we have to make that $1.67=X because you can’t have a repeating decimal when dealing with money. Silly Einstein!