Ratios
Topic Index | Algebra Index | Regents Exam Prep Center


A ratio is a comparison of two quantities.

 

A ratio of one number to another number
 is the quotient of the first number divided by the second number.
(Where the second number is not zero.)

Ratios are most commonly written
 as a fraction.

It's a fraction!

 

A ratio can be written in a variety of ways:

 

Since a ratio can be written as a fraction, it can also be written in any form that is equivalent to that fraction.  All of the following are equivalent:

 

Terms used with ratios:

Continued Ratio:
(the comparison for more than two quantities)

Equivalent Ratios:
(all reduce to the same value)

 

Hint:

When working with ratios such as
2
: 3 : 5, use 2x, 3x, and 5x 
to write an equation!

 

Example:

A teacher graded 180 bonus quizzes during the school year.
  The number of quizzes receiving A's, B's, and C's
were in the ratio of 5 : 3 : 1, respectively.
  Find the number of bonus quizzes that received a grade of A
for the school year.

Solution: 

Represent the number of each grade as 5x, 3x and 1x.
Since there were 180 bonus quizzes in total, we have:
5x + 3x + x = 180
9x = 180
x = 20
Since the 5x represents the number of A's, substitute to find the final answer.
5(20) = 100
100 bonus quizzes received an A   
ANSWER