This lesson about proportions will teach you some very important concepts you need to know. You should review the lesson about ratio before studying this lesson.
Take a look at the image above. Try to measure the ratio of arm's length to height for 5 people that you know. What did you notice? More on this later, so keep reading!
Definition:
Simply put, whenever we put an equal sign between two ratios and the ratio on the left is equal to the ratio on the right, we say that they form a proportion.
3
5

and
6
12

3
5

=
6
12

3
5
= 0.60

6
12
= 0.5

The cross products for
3
5

and
6
12
are

36 is not equal to 30. Therefore,
3
5

and
6
12
do not form a proportion

Another example: Do
10
16

and
5
8
form a proportion ?

If
a
b

=
c
d
is a proportion

3
5

and
6
12

3
5

=
6
12

3
5
= 0.60

6
12
= 0.5

The cross products for
3
5

and
6
12
are

3
5

and
6
12
do not form a proportion

Do
10
16

and
5
8
form a proportion ?

If
a
b

=
c
d
is a proportion

Nov 18, 20 01:20 PM
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