percents and proportions
Percent 
Must-Knows
A percent is the ratio of a number to 100.
You can express 5% as 0.05 or 5/100. 
Percent 
Sentences
4 is what percent of 10?
8 is 40% of what?
What is 20% of 110?
Percent Change
25 --> 35
55 --> 15
Commission
earn = % * sell
You earn 8% commission and sold $545. How much did you earn?
You earn 8% commission and earned $35. How much did you sell?
Tax
final = (1 + %) * original
8% tax on $25
6.5% tax on $32
6% tax, final price = $182
8.5% tax, final price = $52
Discounts
final = (1 = %) * original
10% discount on $24
28% discount on $123
25% discount, final price = $19
35% discount, final price = $110
Successive discounts of 15% and 20% are equal to a single discount of what?
Proportions
(x/3) = (5/7)
(6/x) = (12/10)
(x+1/6) = (5/2)
(x + 1/x - 2) = (4/7)
10 pies feed 74 people, how many people does 7 pies feed?
A scale on a map is 1.5 inches = 6 miles. The distance between two cities is 13 inches. What is the actual distance between the two cities?