The ratio of blue chairs to red chairs in Ms. Vicker's class is 2 to 5. What is the total amount of chairs in her class?

Question

That is all the details.

Answer 1

For this type of problem, there are two other very important details:

  (1)  the number of blue chairs must be a positive integer and the number of red chairs must be a positive integer and the total number of chairs must be a positive integer.

  (2)  some other relationship between blue chairs and red chairs must exist (for example, "9 more red chairs than blue chairs")

 

There may be:

     blue          red             total

      2               5                7

      4              10              14

      6              15              21

      8              20              28

     10             25              35

    ...  (but this gets to be a very big class)

 

Now, it is very important to learn that a "proportion" is "two equal ratios."  That means that there is a value N such that the ratio of blue chairs (2N) to red chairs (5N) is 2:5.  [as a fraction, that is 2N/5N = 2/5].  That's why problems of this type usually give one more clue so you can determine the value of N.