1
Section 81 – Ratios, Proportions, and Proportional Reasoning
Suppose that someone tells you that at a particular school, the ratio of students to teachers is 24:1.
What does that mean?
A
ratio
is a comparison of two quantities and is usually written
b
a
or
a
:
b.
Ratios can represent
parttopart
comparisons
ie,
The ratio of the number of boys to girls is 3:2
Ratios can represent
parttowhole
comparisons
ie.
The ratio of the number of boys to the number of total students is 3:5
Notice that if the ratio of boys to girls is 3:2, that doesn’t tell you the total number of students in the
classroom.
Example
: Find a ratio equivalent to
2:5.
Example
:
Iris has found some dinosaur bones and a fossil footprint.
The length of the footprint
is 40 cm, the length of the thigh bone is 100 cm, and the length of the body is 700 cm.
a)
What is the ratio of the footprint’s length to the thigh bone’s length?
b)
What is the ratio of the footprint’s length to the dinosaur body’s length?
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '12
 LisaJuliano
 Ratios, Ratio, Kirk, following proportions, following percents

Click to edit the document details