Ratio, Proportion, Percent Concepts – Basic College Mathematics for Teachers
K. Elayn Martin-Gay – Page 1
Ratio Comparison of Two numbers Symbols of Comparison: / to : 2/3 2 to3 2:3 4/7 4 to 7 4:7 |
Problem Solving Understand the Problem Translate the Problem Solve the Problem Check the Problem The ratio of boys to girls on a team is 5 to 7. If the team has 35 members then how many boys and girls? |
Proportion Two Equal Ratios or Fractions 2/3 = 4/6 3 to 4 = 9 to 12 3 : 5 = 12 : 20 |
The Law of Proportions Product of Extremes = Product of Means 2/3 = 4/6 2x6 = 3x4 3 to 4 = 9 to12 3x12 = 4x9 3 : 5 = 12:20 3x20 = 5x12 |
Percent means Part of 100 Percent to Fraction 8% = 8/100 17% = 17/100 240% = 2 2/5 |
Percent means Part of 100 Percent to Decimal 7 % = .07 15% = .15 135% = 1.35 |
Percent Problem 25% of N = 4 25/100 = 4 / N 25N = 400 N = 16 What about? N% of 10 is 5 |
Percent Problem 40% of 20 is N 40/100 = N /20 800 = 100N 8 = N What about? N% of 3 is 12 |
Ratio, Proportion, Percent Concepts – Basic College Mathematics for Teachers
K. Elayn Martin-Gay – Page 2
Percent of Increase A score was increased from 60 to 80. What percent of increase? 60 is increased 20 to be 80 Amount increased
over original number! 20 / 60 = N / 100 |
Percent of Decrease A price was decreased from $5 to $4. What percent of decrease? $5 is decreased $1 to be $4 Amount of decreased
over original number! 1 / 5 = N /100 |
Commission or TipFifteen Percent is considered to be a good commission or tip! Sales of $200 expects a commission or tip of how much? 15% of $200 is N 15/100 = N/200 N = $30 A good commission & tip! |
Discount or Sale PriceAn item is Discounted or has a Sale Price lower then original. An original Price of $35 is discounted 20%. What is amount of discount & sale price? 20% of $35 is N 20/100 = N/35 Discount = $7 & Sale Price = $28 |
Simple Interest Interest = Principal x Rate x Time P = $2000 R = 3% T = 4 years I = 2000 x .03 x 4 I = $240 |
Savings Account Savings = Principal + Interest P = $400 R = 6% T= 5 years I = 400 x .06 x 5 = $120 Savings = $400 + $120 = $520 |
|
|