Ratios and proportions
Definitions
• Ratio: is a comparison of two numbers by
division.
• Example: x to y; x:y; x/y or x divided by y
• Means-Extremes Property
of Proportions: In a proportion, the
product of extremes is equal to the product
of the means.
Example: if a/b =c/d, then ad=bc
Definitions
• Scale: is a ratio used when making a
model to represent something that is too
large or too small to conveniently be
drawn at actual size.
Example
• 3/6 = x/2, here x = 1. Cross multiply to get
the answer, so 3*2 = 6*x, which is
• 6 = 6*x, divide both sides by 6 and
• X=1
Solve
• 4/7 = n/14
• Answer, n = 2
• 12/20 = r/45
• Answer, r = 2
• Is the following a true proportion?
• 36/45 = 32/40
• Answer 1440 = 1440, so yes.