7.1 Day 1 ­ Writing and Solving Proportions.notebook
7.1: Writing & Solving Proportions
March 03, 2014
Date: 3/3
A ratio is a comparison of two quantities by division. You can write the
ratio of two numbers in three ways:
Ex 1). A pigmy rattlesnake has an average length of 18 in., while a
Western diamondback rattlesnake averages a length of 5 ft 6 in. What is
the ratio of the length of a pigmy rattlesnake to the length of a Western
diamondback rattlesnake?
7.1 Day 1 ­ Writing and Solving Proportions.notebook
March 03, 2014
Ex 2). Write the ratio of the first measurement to the second measurement.
a) length of car: 14 ft 10 in
length of model car: 8 in
b) weight of car: 2900 lb
weight of model car: 8 oz
7.1 Day 1 ­ Writing and Solving Proportions.notebook
March 03, 2014
Ex 3). There are 238 juniors at a high school. The ratio of girls to boys in
the junior class to is 3 : 4. How many juniors are girls? How many are
boys?
Ex 4). The measures of two complementary angles are in the ratio 1 : 3.
What are the measures of the angles?
Ex 5). The measures of two supplementary angles are in the ratio 1 : 4.
What are the measures of the angles?
7.1 Day 1 ­ Writing and Solving Proportions.notebook
March 03, 2014
An equation that states that two ratios are equal is a proportion
Solving Proportions
7.1 Day 1 ­ Writing and Solving Proportions.notebook
Ex 6). Solve each proportion.
a)
b)
c)
d)
March 03, 2014
7.1 Day 1 ­ Writing and Solving Proportions.notebook
March 03, 2014
Ex 7). Write and solve a proportion.
a) About 45 of every 300 apples picked at Newbury Apple Orchard are
rotten. If 3560 apples were picked one week, about how many apples
were rotten?
b) A grocer orders 800 gal of milk each week. He throws out about 64
gal of spoiled milk each week. Of the 9600 gal of milk he ordered over
three months, about how many gallons of spoiled milk were thrown out?
7.1 Day 1 ­ Writing and Solving Proportions.notebook
March 03, 2014
An extended ratio compares three (or more) numbers.
apples oranges bananas
Ex: Suppose an extended ratio of
2
3
5
apples oranges to bananas is given as 2 : 3 : 5.
4
6
10
6
9
15
8
12
20
7.1 Day 1 ­ Writing and Solving Proportions.notebook
March 03, 2014
Ex 1). Using an extended ratio:
a) The lengths of the sides of a triangle are in the extended ratio 2 : 4 : 5.
The perimeter of the triangle is 77 in. What is the length of the longest
side?
7.1 Day 1 ­ Writing and Solving Proportions.notebook
March 03, 2014
b) The lengths of the sides of a triangle are in the extended proportion
3 : 4 : 10. If the length of the shortest side is 9 in., what is the perimeter of
the triangle?
7.1 Day 1 ­ Writing and Solving Proportions.notebook
Properties of Proportions
(1)
(2)
(3)
March 03, 2014
7.1 Day 1 ­ Writing and Solving Proportions.notebook
Ex 2). In the diagram,
proportion
March 03, 2014
What ratio completes the equivalent
? Use one of the Properties of Proportions
to justify your answer.
7.1 Day 1 ­ Writing and Solving Proportions.notebook
Homework:
pg. 459 #9 ­ 27, 34, 36
Quiz (7.1 ­ 7.3) ­ Friday
March 03, 2014