Post on 07-Jan-2016
description
How to find proportions
By: deonta brown
What a proportion is
• A proportion is simply a statement that two ratios are equal. The following proportion is read as "twenty is to twenty-five as four is to five.“
20
25 4
5
How to start it
•It can be written in two ways: as two equal fractions a/b = c/d; or using a colon, a:b = c:d
a
b
c
d
Step 1
•The following proportion is read as "twenty is to twenty-five as four is to five.“
20
25
4
5
Step 2
•cross products of a proportion, we multiply the outer terms and the middle terms
Step 2
•Here, 20 and 5 and 25 and 4 Since the cross products are both equal to one hundred, we know that these ratios are equal and that this is a true proportion.
• 20x5=25x4
• cross products 100=100
20
25
4
5