This lesson is part of a series of lessons for the quantitative reasoning section of the GRE revised General Test. In this lesson, we will learn:
A ratio is a comparison between two quantities of the same kind, for example:
There are 3 red sweets and 5 yellow sweets in the box. We can say the ratio of red sweets to yellow sweets is 3 to 5. Ratio can be written with the symbol ':' or as a fraction.
'3 to 5' can be written as '3:5' or
Like fractions, ratios can be reduced to lowest terms. For example, if there are 6 red sweets and 10 yellow sweets in the box, then the ratio of the numbers of red sweets to yellow sweets is 6:10 which can be reduced to 3:5.
A three-term ratio can be used to compare three quantities, for example:
There are 5 red sweets, 15 yellow sweets and 30 blue sweets in the box
5 to 15 to 30 = 5:15:30 which can be reduced (divide by 5) to 1:3:6
A proportion is an equation relating two ratios.
To solve a problem involving ratios, you can often write a proportion and solve it by cross multiplication.
If two pens cost $1.50, how many pens can you buy with $9.00?
You can buy 12 pens
If the ratio of the number of men to the number of women on a committee of 20 members is 3 to 2, how many members of the committee are women?
men : women : total = 3 : 2 : 5
There are 8 women in the committee.
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