Ratio and Proportion
Ratio - Given two numbers x and y, y  0, a ratio is
the quotient x divided by y. A ratio can be written
as x to y, x:y, or x/y. All of these ratios are read x
to y.
Extended Ratios – Ratios that compare three or
more numbers, such as a:b:c.
Proportion - A proportion is the equality of two
ratios. In symbols, a/b = c/d or a:b = c:d. It is
read a is to b as c is to d.
The country with the longest school year is China
with 251 days. Find the ratio of school days to total
days in a year for China to the nearest tenth. (Use
365 as the number of days in a year.)
Answer: 0.7
Multiple- Choice Test Item
In a triangle, the ratio of the measures of three sides
is 3:4:5, and the perimeter is 42 feet. Find the
measure of the longest side of the triangle.
A 10.5 ft
Answer: C
B 14 ft
C 17.5 ft
D 37 ft
Ratio and Proportion
Terms - Each number in a proportion is called a
term.
Extremes - The first and fourth terms in a proportion
are called the extremes.
Means - The second and third terms in a proportion
are called the means.
Proportions are solved by cross-multiplying - which
is multiplying the means by each other and the
extremes by each other.
Ratio and Proportion
Properties of Proportions
1. Means-extremes property
• a/b = c/d is equivalent to a  d=b  c.
2. Means or extremes can be interchanged.
• a/b = c/d is equivalent to a/c = b/d and a/b =
c/d is equivalent to d/b = c/a.
Solve each proportion.
a.
Answer: 4.5
b.
Answer: 9
Two large cylindrical containers are in proportion.
The height of the larger container is 25 meters with
a diameter of 8 meters. The height of the smaller
container is 7 meters. Find the diameter of the
smaller container.
Answer: 2.24 m