Download presentation

1
**Percent Increase and Decrease**

2-10 Percent Increase and Decrease Holt Algebra 1 Warm Up Lesson Presentation Lesson Quiz

2
**Warmup: Which is a better deal?**

Get Your Calculator Warmup: Which is a better deal? A DVD costs $20. Sales tax is 8% and you receive a 10% discount. Should you calculate the tax first then the discount or the other way around?

3
Discount first: ($20)(.10) = $2 20 – 2 = $18 Tax first: ($20)(.08) = $1.60 = $21.60 Now Discount: ($21.60)(.10) = $2.16 21.60 – 2.16 = $19.44 Now Tax: ($18)(.08) = $1.44 = $19.44 Which is a better deal for you? Which is a better deal for the business?

4
**Warm Up 1. Find 30% of 40. 2. Find 28% of 60. 12 Solve for x.**

5. 20 is what percent of 80? 6. 36 is what percent of 30? 12 16.8 0.44 38 25% 120%

5
Objective Find percent increase and decrease.

6
**Vocabulary percent change percent increase percent decrease discount**

markup

7
A percent change is an increase or decrease given as a percent of the original amount. Percent increase describes an amount that has grown and percent decrease describes an amount that has be reduced. Notes on next slide

8
**Definition: (write this down)**

Percent of Change Definition: (write this down) Percent of Change = Difference Original Which Means: % Increase or % Decrease Using this formula, your answer comes out as a decimal. Just multiply by 100 to change to a percent

9
**Example 1A: Finding Percent Increase and Decrease**

Find each percent change. Tell whether it is a percent increase or decrease. From 8 to 10 Simplify the numerator. Simplify the fraction. = 0.25 = 25% Write the answer as a percent. 8 to 10 is an increase, so a change from 8 to 10 is a 25% increase.

10
Helpful Hint Before solving, decide what is a reasonable answer. For Example 1A, 8 to 16 would be a 100% increase. So 8 to 10 should be much less than 100%.

11
**Example 1B: Finding Percent Increase and Decrease**

Find the percent change. Tell whether it is a percent increase or decrease. From 75 to 30 Simplify the fraction. Simplify the numerator. = 0.6 = 60% Write the answer as a percent. 75 to 30 is a decrease, so a change from 75 to 30 is a 60% decrease.

12
**Example 2: Finding Percent Increase and Decrease**

A. Find the result when 12 is increased by 50%. 0.50(12) = 6 Find 50% of 12. This is the amount of increase. =18 It is a percent increase, so add 6 to the original amount. 12 increased by 50% is 18. B. Find the result when 55 is decreased by 60%. Find 60% of 55. This is the amount of decrease. 0.60(55) = 33 55 – 33 = 22 It is a percent decrease so subtract 33 from the the original amount. 55 decreased by 60% is 22.

13
**Common application of percent change are discounts and markups.**

A discount is an amount by which an original price is reduced. discount = % of original price final price = – A markup is an amount by which a wholesale price is increased. final price = wholesale cost markup + = % of

14
Example 3: Discounts The entrance fee at an amusement park is $35. People over the age of 65 receive a 20% discount. What is the amount of the discount? How much do people over 65 pay? Method 1 A discount is a percent decrease. So find $35 decreased by 20%. Find 20% of 35. This is the amount of the discount. 0.20(35) = 7 35 – 7 = 28 Subtract 7 from 35. This is the entrance fee for people over the age of 65.

15
Example 3A: Discounts Method 2 Subtract the percent discount from 100%. 100% – 20% = 80% People over the age of 65 pay 80% of the regular price, $35. 0.80(35) = 28 Find 80% of 35. This is the entrance fee for people over the age of 65. 35 – 28 = 7 Subtract 28 from 35. This is the amount of the discount. By either method, the discount is $7. People over the age of 65 pay $28.00.

16
Helpful Hint Before solving, decide what is a reasonable answer. For example 3A, a 10% discount is $3.50 off. So a 20% discount would be more than $2 off.

17
Example 3B: Discounts A student paid $31.20 for art supplies that normally cost $ Find the percent discount . Think: is what percent of 52.00? Let x represent the percent. $52.00 – $31.20 = $20.80 20.80 = x(52.00) Since x is multiplied by 52.00, divide both sides by to undo the multiplication. 0.40 = x 40% = x Write the answer as a percent. The discount is 40%

18
Example 4: Markups The wholesale cost of a DVD is $7. The markup is 85%. What is the amount of the markup? What is the selling price? Method 2 Method 1 A markup is a percent increase. So find $7 increased by 85%. Add percent markup to 100% Find 85% of 7. This is the amount of the markup. 100% + 85% = 185% The selling price is 185% of the wholesale price, 7. 0.85(7) = 5.95 1.85(7) = 12.95 = 12.95 Find 185% of 7. This is the selling price. Add to 7. This is the selling price. 12.95 7 = 5.95 Subtract from This is the amount of the markup. By either method, the amount of the markup is $5.95. The selling price is $12.95.

19
Lesson Quiz: Part 1 Find each percent change. Tell whether it is a percent increase or decrease. 1. from 20 to 28. 2. from 80 to 62. 3. from 500 to 100. 4. find the result when 120 is increased by 40%. 5. find the result when 70 is decreased by 20%. 40% increase 22.5% decrease 80% decrease 168 56

20
**Lesson Quiz: Part 2 80% decrease 1. from 500 to 100. 168**

Find the percent change. Tell whether it is a percent increase or decrease. 80% decrease 1. from 500 to 100. 2. find the result when 120 is increased by 40%. 168 Find each percent change. Tell whether it is a percent increase or decrease. 3. A movie ticket costs $9. On Mondays, tickets are 20% off. What is the amount of discount? How much would a ticket cost on a Monday? 4. A bike helmet cost $24. The wholesale cost was $15. What was the percent of markup? $1.80; $7.20 60%

Similar presentations

© 2024 SlidePlayer.com Inc.

All rights reserved.

To make this website work, we log user data and share it with processors. To use this website, you must agree to our Privacy Policy, including cookie policy.

Ads by Google