# Ratio, Percent , Proportion - PowerPoint PPT Presentation

Pg 16. Ratio, Percent , Proportion. EQ: How do you use percentages to calculate tax, tip, commission, mark-ups, discounts and other real world contexts? OBJ: 1.01. Problem of the Day: Is the percent of decrease from 80 to 50 the same as the percent of increase from 50 to 80?

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Ratio, Percent, Proportion

EQ: How do you use percentages to calculate tax, tip, commission, mark-ups, discounts and other real world contexts?

Problem of the Day:

Is the percent of decrease from 80 to 50 the same as the percent of increase from 50 to 80?

EQ: How do you use percentages to calculate tax, tip, commission, mark-ups, discounts and other real world contexts?

Problem of the Day:

Jon and Amie each purchased a pair of shoes during the annual sale at the Shoe Factory. All shoes were priced 40% off the original price. If Jon paid $35 for his shoes, what was the original price? If Aime bought a pair of shoes originally priced at $79, what was the sale price?

Tax: Additional cost which goes to the government

Tip: Additional cost which goes to the service

Commission: A form of payment for service

Mark-up: Additional cost added by the manufacturer

A percent can be used to describe an amount of change. The percent of change is the amount, stated as a percent, that a number increases or decreases. If the amount goes up, it is a percent of increase. If the amount goes down, it is a percent of decrease.

You can find the percent of change by using the following formula.

amount of change

Percent of change =

When a number is decreased, subtract the new amount from the original amount to find the amount of change.

Additional Example 1A: Finding Percent of Change

Find the percent of change. Round answers to the nearest tenth of a percent, if necessary.

A. 65 is decreased to 38.

Find the amount of change.

Substitute values into

percent of change =

Write as a percent. Round.

The percent of decrease is about 41.5%.

When a number is increased, subtract the original amount from the new amount.

Additional Example 1B: Finding Percent of Change

Find the percent of change. Round answers to the nearest tenth of a percent, if necessary.

B. 41 is increased to 92.

Find the amount of change.

Substitute values into

Percent of change =

Write as a percent. Round.

The percent of increase is about 124.4%

Find the percent of change. Round answers to the nearest tenth of a percent, if necessary.

A. 70 is decreased to 45.

Find the amount of change.

Substitute values into

percent of change =

Write as a percent. Round.

The percent of decrease is about 35.7%.

Find the percent of change. Round answers to the nearest tenth of a percent, if necessary.

B. 37 is increased to 56.

Find the amount of change.

Substitute values into

Percent of change =

Write as a percent. Round.

The percent of increase is about 51.4%

The regular price of a bicycle helmet is $42.99. It is on sale for 20% off.

A. Find the actual amount of the discount.

Think: 20% of $42.99 is what number?

Write the percent as a decimal.

Round to the nearest cent.

The discount is $8.60.

B. Find the sale price.

Subtract the discount from the regular price.

$42.99 вЂ“ $8.60 = $34.39

The sale price is $34.39

Try This to find the actual amount of change.: Example 2A & 2B

The regular price of a computer game is $49.88. It is on sale for 15% off.

A. Find the actual amount of the discount.

Think: 15% of $49.88 is what number?

Write the percent as a decimal.

Round to the nearest cent.

The discount is $7.48.

B. Find the sale price.

Subtract the discount from the regular price.

$49.88 вЂ“ $7.48 = $42.40

The sale price is $42.40

Additional Example 3: to find the actual amount of change.Business Application

A boutique buys hand-painted T-shirts for $12.60 each and sells them at a 110% increase in price. What is the selling price of the T-shirts?

First find the actual amount of increase.

Think: 110% of $12.60 is what number?

Write the percent as a decimal.

The amount of increase is $13.86. Now find the selling price.

Think: retail price = wholesale price + amount of increase.

The retail price of the hand-painted T-shirts is $26.46 each.

Insert Lesson Title Here to find the actual amount of change.

Try This: Example 3

William makes T-shirts for $7.00 each and sells them after a price increase of 125%. What is the selling price of the T-shirts?

First find the actual amount of increase.

Think: 125% of $7.00 is what number?

Write the percent as a decimal.

The amount of increase is $8.75. Now find the selling price.

Think: retail price = wholesale price + amount of increase.

The retail price of the T-shirts is $15.75 each.

Insert Lesson Title Here to find the actual amount of change.

Find each percent of change.

1. 10 is increased to 12.

2. 25 is increased to 45.

3. 10 is decreased to 1.

4. 120 is decreased to 90.

5. A backpack that sells for $42 is on sale for 25% off. Find the amount of discount and the sale price.