Section 3.5
Write Ratios and Proportions
GOAL: FIND RATIOS
AND WRITE AND
SOLVE PROPORTIONS
Rate: A function that compares two quantities
measured in different units
Proportion:
An equation that states that two
ratios are equivalent
The ratio of two quantities, a and b, where b is not equal to
zero, can be written in 3 ways:
a to b
1._____
a:b
2._____
a
b
3._____
Ex. 1: A person makes 6 long distance calls and 15 local calls.
1a. Find the ration of long distance calls to local calls:
long distance calls
6

 2
local calls
15
5
1b. Find the ratio of long distance calls to all calls:
long distance calls
2
6


all calls
21 7
Ex. 2: Ken and Heather are selling tickets to their
schools talent show. Ken sold 36 tickets, and Heather
sold 44 tickets. Find the specified ratio.
2a. The number of tickets Ken sold to the number of tickets Heather
sold:
36

44
9

11
2b. The number of tickets Heather sold to the number of tickets they
both sold:
11
44


20
80
5 y  45
5
5
y9
4c  252
4
4
c  63
8a  224
8
8
a  28
An empty swimming pool is being filled with
water. After 5 minutes the pool has 400
gallons of water. If the pool has a volume of
11,200 gallons, how long does it take to fill the
empty pool?
time
volume
5 min
x min

400 gal 11,200 gal
140min
400 x  56000