Percentage

Percentage

1. Simple Percentage Problems

   • A test has 20 questions. If peter gets 80% correct, how many questions did peter missed? The number of correct answers is 80% of 20 or 80/100 × 20 80/100 × 20 = 0.80 × 20 = 16 Recall that 16 is called the percentage. It is the answer you get when you take the percent of a number Since the test has 20 questions and he got 16 correct answers, the number of questions he missed is 20 − 16 = 4 Peter missed 4 questions

2. Reverse Percentages

   • Sometimes a question will ask you to work backwards and find the original price of something after the price has increased. A new car falls in value by 30% in a year. After a year, it is worth $8,400. Find the price of the car when it was new Original price = 100% Second-hand price = 100% - 30% = 70% 1% of original price = $8,400 ÷ 70 Original price = 100% = 100 x 1% = 100 x($8,400÷ 70) = $12,000

3. Discount and GST

   • When you offer your customers a discount on the selling price of your goods and services, GST is chargeable on the net discounted price. In a candy store, a $5.00 jar of candy is labeled, "50% off." What is the discount? What is the sale price of the jar of candy? Discount = 0.50 x $5.00 = $2.50 Sale price = $5.00 - $2.50 = $2.50 Before adding GST at 7%, a particular item's cost is $100. What is the total cost including GST? Total with GST = Cost without GST + 7% of cost without GST = 100 + 0.07 × 100 = 107

4. Percentage Increase And Decrease

   • Often prices are increased or decreased by a percentage. Katie earns $40 per week for her part-time job. She is to be given a 5% pay rise. How much will she earn per week after the pay rise? 5% of $40 = 5/100 × £40 = $2 New pay = $40 + $2 = $42