Lesson14:&&MultiEStep&Ratio&Problems&& ·...

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Lesson 14: Multi-‐Step Ratio Problems Date: 7/26/15

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NYS COMMON CORE MATHEMATICS CURRICULUM 7•1 Lesson 14

Lesson 14: Multi-‐Step Ratio Problems

Student Outcomes

§ Students solve multi-‐step ratio problems including fractional markdowns, markups, commissions, fees, etc.

Lesson Notes In this lesson, students solve multi-‐step ratio problems including fractional markdowns, fractional commissions, fees, and discounts. Problems with similar context that apply percent concepts will be introduced in Modules 2 and 4. Modeling the problems with a tape diagram will help students visualize the relationships among features of a scenario.

Classwork

Example 1 (12 minutes): Bargains

Begin this lesson by discussing advertising. Share with students that businesses will create an advertisement that will encourage consumers to come to their business in order to purchase their products. Many businesses subscribe to the idea that if a consumer thinks that he or she is saving money, then the consumer will be more motivated to purchase the product.

Have students verbalize how they would determine the sale prices with a discount rate of !!

off the original price of the shirt, !! off the original price of pants, and !

! off the original price

of the shoes.

Students should provide an idea that is similar to this: discount price = original price – rate times the original price.

Example 1: Bargains

Peter’s Pants Palace advertises the following sale: Shirts are 𝟏𝟐 off the original price; pants are

𝟏𝟑 off

the original price, and shoes are 𝟏𝟒 off the original price.

a. If a pair of shoes costs $𝟒𝟎, what is the sales price?

Method 1: Tape Diagram

After 𝟏𝟒 of the price is taken off the

original price, the discounted price is $𝟑𝟎.

Method 2: Subtracting 𝟏𝟒 of the price

from the original price

𝟒𝟎 −𝟏𝟒 (𝟒𝟎)

𝟒𝟎 − 𝟏𝟎

$𝟑𝟎

Method 3: Finding the fractional part of the price being paid by subtracting 𝟏𝟒 of the price from 𝟏 whole

𝟏 −𝟏𝟒 𝟒𝟎

𝟑𝟒 𝟒𝟎

$𝟑𝟎

Scaffolding:

§ Remind students that “of” in mathematics is an operational word for multiply.

§ Note that students may find the amount of the discount and forget to subtract it from the original price.

§ Equate the meanings of a markdown price, a discount price, and a sale price.

MP.1

$10 $10 $10 $10

$𝟒𝟎



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b. At Peter’s Pants Palace, a pair of pants usually sells for $𝟑𝟑.𝟎𝟎. What is the sale price of Peter’s pants?

Method 1: Tape Diagram

$𝟑𝟑 ÷ 𝟑 = $𝟏𝟏 𝟐 $𝟏𝟏 = $𝟐𝟐

Method 2: Use the given rate of discount, multiply by the price, and then subtract from the original price.

𝟑𝟑 −𝟏𝟑 𝟑𝟑 = 𝟑𝟑 − 𝟏𝟏 = $𝟐𝟐

The consumer pays 𝟐𝟑 of the

original price.

Method 3: Subtract the rate from 𝟏 whole, then multiply that rate by the original price.

𝟏 −𝟏𝟑 =

𝟐𝟑

𝟐𝟑 𝟑𝟑 = $𝟐𝟐.𝟎𝟎

Use questioning to guide students to develop the methods above. Students do not need to use all three methods, but should have a working understanding of how and why they work in this problem.

Example 2 (3 minutes): Big Al’s Used Cars

Have students generate an equation that would find the commission for the salesperson.

Example 2: Big Al’s Used Cars

A used car salesperson receives a commission of 𝟏𝟏𝟐

of the sales price of the car for each car he sells.

What would the sales commission be on a car that sold for $𝟐𝟏,𝟗𝟗𝟗?

Commission = 𝟐𝟏,𝟗𝟗𝟗 𝟏𝟏𝟐 = $𝟏𝟖𝟑𝟑.𝟐𝟓

Example 3 (8 minutes): Tax Time

When solving the problem, develop the understanding for the use of 1 !! to find the markup and the use of !

! to find the

markdown.

Example 3: Tax Time

As part of a marketing plan, some businesses mark up their prices before they advertise a sales event. Some companies use this practice as a way to entice customers into the store without sacrificing their profits.

A furniture store wants to host a sales event to improve its profit margin and to reduce its tax liability before its inventory is taxed at the end of the year.

How much profit will the business make on the sale of a couch that is marked up by 𝟏𝟑 and then sold at a

𝟏𝟓 off discount if

the original price is $𝟐,𝟒𝟎𝟎?

Markup: $𝟐,𝟒𝟎𝟎 + $𝟐,𝟒𝟎𝟎 𝟏𝟑 = $𝟑,𝟐𝟎𝟎 or $𝟐,𝟒𝟎𝟎 𝟏 𝟏𝟑 = $𝟑,𝟐𝟎𝟎

Markdown: $𝟑,𝟐𝟎𝟎 − $𝟑,𝟐𝟎𝟎 𝟏𝟓 = $𝟐,𝟓𝟔𝟎 or $𝟑,𝟐𝟎𝟎 𝟒

𝟓 = $𝟐,𝟓𝟔𝟎

Profit = sales price − original price = $𝟐,𝟓𝟔𝟎 − $𝟐,𝟒𝟎𝟎 = $𝟏𝟔𝟎.𝟎𝟎

$11 $11 $11

Scaffolding:

Discuss the meaning of a commission as some students may not be familiar with this concept.



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Example 4 (7 minutes): Born to Ride

Explain that a whole plus the fractional increase will give 1 + !!= !

! of the original price.

Example 4: Born to Ride

A motorcycle dealer paid a certain price for a motorcycle and marked it up by 𝟏𝟓 of the price he paid. Later, he sold it for

$𝟏𝟒,𝟎𝟎𝟎. What is the original price?

Let x represent the original price the dealer paid for the motorcycle.

Exercise

Exercise

Party Central rents Karaoke machines for private parties. The rental is for 24 hours. An additional fee of 𝟏𝟖 of the rental

amount is charged for each day the Karaoke machine is returned late. Carlene rented a Karaoke machine on Saturday for her birthday party but did not return it until Monday. What was the rental price excluding the one day late fee if the total charge was $46.80?

Note: A Karaoke machine displays the words of a song on a video screen so people can sing along to the song’s music.

𝒙 +𝟏𝟓 𝒙 = 𝟏𝟒, 𝟎𝟎𝟎

𝟔𝟓 𝒙 = 𝟏𝟒, 𝟎𝟎𝟎

!𝟓𝟔!𝟔𝟓 𝒙 = !

𝟓𝟔!𝟏𝟒,𝟎𝟎𝟎

𝒙 = $𝟏𝟏,𝟔𝟔𝟔. 𝟔𝟕

𝟔𝟓 𝒙 = 𝟏𝟒, 𝟎𝟎𝟎

!𝟓𝟔! !

𝟔𝟓𝒙! =

(𝟏𝟒, 𝟎𝟎𝟎) !𝟓𝟔!

𝒙 = $𝟏𝟏,𝟔𝟔𝟔.𝟔𝟕

Original Price 𝑥

Markup

$𝟏𝟒, 𝟎𝟎𝟎

𝟏𝟓 𝒙

𝟏𝟓𝒙

𝟏𝟓 𝒙

𝟏𝟓𝒙

𝟏𝟓𝒙

𝟏𝟓 𝒙



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If x represents the rental price, then 𝒙 + 𝟏𝟖𝒙 = $𝟒𝟔.𝟖𝟎 can be used to find the late fee.

𝒙 +𝟏𝟖 𝒙 = 𝟒𝟔.𝟖𝟎

𝟗𝟖 𝒙 = 𝟒𝟔

𝟒𝟓

𝟖𝟗

𝟗𝟖 𝒙 =

𝟖𝟗

𝟐𝟑𝟒𝟓

𝒙 = 𝟒𝟏𝟑𝟓

𝒙 = $𝟒𝟏.𝟔𝟎

C losing (5 minutes)

§ Name at least two methods used to find the solution to a fractional markdown problem.

ú Find the fractional part of the markdown, and subtract it from the original price.

ú Use a tape diagram to determine the value each part represents, and then subtract the fractional part from the whole.

§ Compare and contrast a commission and a discount price?

ú The commission and the discount price are both fractional parts of the whole. The difference between them is that commission is found by multiplying the commission rate times the sale, while the discount is the difference between 1 and the fractional discount multiplied by the original price.

Lesson Summary

§ Discount price = original price − rate × original price OR (𝟏− rate) × original price

§ Commission = rate × total sales amount

§ Markup price = original price + rate × original price OR (𝟏+ rate) × original price

Rental Price 𝑥

Late Fee

$𝟒𝟔.𝟖𝟎 Total Amount

𝟏𝟖 𝒙

𝟏𝟖 𝒙

𝟏𝟖 𝒙

𝟏𝟖𝒙

𝟏𝟖 𝒙

𝟏𝟖𝒙

𝟏𝟖 𝒙

𝟏𝟖 𝒙

𝟏𝟖 𝒙



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Exit Ticket (5 minutes)

Name ___________________________________________________ Date____________________

Lesson 14: Multi-‐Step Ratio Problems

Exit Ticket 1. A bicycle shop advertised all mountain bikes priced at a !

! discount.

a. What is the amount of the discount if the bicycle originally cost $327?

b. What is the discount price of the bicycle?

c. Explain how you found your solution to part (b).

2. A hand-‐held digital music player was marked down by !! of the original price.

a. If the sales price is $128.00, what is the original price?



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b. If the item was marked up by !! before it was placed on the sales floor, what was the price that the store paid

for the digital player?

c. What is the difference between the discount price and the price that the store paid for the digital player?

Circle one:

I’m on my way. I’ve got it. I can teach it!



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Exit Ticket Sample Solutions

1. A bicycle shop advertised all mountain bikes priced at a 𝟏𝟑 discount.

a. What is the amount of the discount if the bicycle originally costs $𝟑𝟐𝟕?

𝟏𝟑($𝟑𝟐𝟕) = $𝟏𝟎𝟗 discount

b. What is the discount price of the bicycle?

𝟐𝟑($𝟑𝟐𝟕) = $𝟐𝟏𝟖 discount price. Methods will vary.

c. Explain how you found your solution to part (b).

Answers will vary.

2. A hand-‐held digital music player was marked down by 𝟏𝟒 of the original price.

a. If the sales price is $𝟏𝟐𝟖.𝟎𝟎, what is the original price?

𝒙 −𝟏𝟒𝒙 = 𝟏𝟐𝟖

𝟑𝟒𝒙 = 𝟏𝟐𝟖

𝒙 = $𝟏𝟕𝟎.𝟔𝟕

𝒙 Original Price

Markdown Sale Price $128

𝟏𝟒 𝒙

𝟏𝟒 𝒙

𝟏𝟒 𝒙

𝟏𝟒𝒙

Discount Price Discount

$𝟑𝟐𝟕 Original Price



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b. If the item was marked up by 𝟏𝟐 before it was placed on the sales floor, what was the price that the store paid

for the digital player?

𝒙 +𝟏𝟐 𝒙 = 𝟏𝟕𝟎.𝟔𝟕

𝟑𝟐 𝒙 = 𝟏𝟕𝟎.𝟔𝟕

𝒙 = $𝟏𝟏𝟑.𝟕𝟖

c. What is the difference between the discount price and the price that the store paid for the digital player?

$𝟏𝟐𝟖 − $𝟏𝟏𝟑.𝟕𝟖 = $𝟏𝟒.𝟐𝟐

Model Problems

1. A pair of jeans are on sale for !! off the original price of $45. What is the sale price?

Solution:

Subtract the discount rate from 1 whole.

𝟏 −𝟐𝟓 =

𝟑𝟓

Then multiply that rate by the original price. 𝟑𝟓 𝟒𝟓 = 𝟐𝟕

The sale price is $27.

$𝟏𝟕𝟎. 𝟔𝟕

Markup Price the Store Paid

𝒙

𝟏𝟐𝒙

𝟏𝟐 𝒙

𝟏𝟐𝒙

$𝟒𝟓 Original Price

Sale Price Discount



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2. During an end-‐of-‐season sale, a jacket sold for $54. What was the original price if the discount was !! off the

original price?

Solution:

23𝑥 = 54

3223𝑥 =

3254

𝑥 = 81

The original price of the jacket was $81.

3. A sporting goods store is planning a !! off sale on soccer balls. Before they calculate the sale price, they mark

up the balls by !! of their initial cost of $30. What profit will the store make on the sale of the soccer balls?

𝟑𝟓𝟑𝟎 = $𝟏𝟖 𝒎𝒂𝒓𝒌𝒖𝒑 𝒇𝒓𝒐𝒎 𝒕𝒉𝒆 𝒊𝒏𝒊𝒕𝒊𝒂𝒍 𝒄𝒐𝒔𝒕

𝟑𝟎 + 𝟏𝟖 = $𝟒𝟖 𝒑𝒓𝒊𝒄𝒆 𝒃𝒆𝒇𝒐𝒓𝒆 𝒕𝒉𝒆 𝒔𝒂𝒍𝒆 𝟏𝟒𝟒𝟖 = $𝟏𝟐 𝒅𝒊𝒔𝒄𝒐𝒖𝒏𝒕

𝟒𝟖 − 𝟏𝟐 = $𝟑𝟔 𝒔𝒂𝒍𝒆 𝒑𝒓𝒊𝒄𝒆 or 𝟑𝟒𝟒𝟖 = $𝟑𝟔

𝑝𝑟𝑜𝑓𝑖𝑡 = 𝑠𝑎𝑙𝑒 𝑝𝑟𝑖𝑐𝑒 − 𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝑐𝑜𝑠𝑡 = 36 − 30 = $6 𝑝𝑟𝑜𝑓𝑖𝑡.

Sale Price $54

Discount

𝒙 Original Price

𝟏𝟑𝒙

𝟏𝟑𝒙

𝟏𝟑 𝒙



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Problem Set Sample Solutions

1. A salesperson will earn a commission equal to 𝟏𝟑𝟐

of the total sales. What is the commission earned on sales totaling

$𝟐𝟒,𝟎𝟎𝟎?

𝟏𝟑𝟐 $𝟐𝟒,𝟎𝟎𝟎 = $𝟕𝟓𝟎

2. DeMarkus says that a store overcharged him on the price of the video game he bought. He thought that the price

was marked 𝟏𝟒 of the original price, but it was really

𝟏𝟒 off the original price. He misread the advertisement. If the

original price of the game was $𝟒𝟖, what is the difference between the price that DeMarkus thought he should pay and the price that the store charged him?

𝟏𝟒 of $𝟒𝟖 = $𝟏𝟐 (the price DeMarkus thought he should pay);

𝟏𝟒 off $𝟒𝟖 = $𝟑𝟔; Difference between prices

$𝟑𝟔 − $𝟏𝟐 = $𝟐𝟒

3. What is the cost of a $𝟏,𝟐𝟎𝟎 washing machine after a discount of 𝟏𝟓 the original

price?

𝟏 − 𝟏𝟓 𝟏𝟐𝟎𝟎 = $𝟗𝟔𝟎 or 𝟏𝟐𝟎𝟎 − 𝟏

𝟓 (𝟏𝟐𝟎𝟎) = $𝟗𝟔𝟎 or 𝟒𝟓 𝟏𝟐𝟎𝟎 = $𝟗𝟔𝟎

4. If a store advertised a sale that gave customers a 𝟏𝟒 discount, what is the fractional

part of the original price that the customer will pay?

𝟏 − 𝟏𝟒= 𝟑

𝟒 of original price

5. Mark bought an electronic tablet on sale for 𝟏𝟒 off the original price of $𝟖𝟐𝟓.𝟎𝟎. He

also wanted to use a coupon for 𝟏𝟓 off the sales price. Before taxes, how much did Mark pay for the tablet?

$𝟖𝟐𝟓 𝟑𝟒

= $𝟔𝟏𝟖.𝟕𝟓, then $𝟔𝟏𝟖.𝟕𝟓 𝟒𝟓

= $𝟒𝟗𝟓

6. A car dealer paid a certain price for a car and marked it up by 𝟕𝟓 of the price he paid. Later he sold it for $𝟐𝟒,𝟎𝟎𝟎.

What is the original price?

𝒙 + 𝟕𝟓𝒙 = $𝟐𝟒,𝟎𝟎𝟎, 𝟏𝟐

𝟓𝒙 = $𝟐𝟒, 𝟎𝟎𝟎, 𝒙 = $𝟏𝟎,𝟎𝟎𝟎

7. Joanna ran a mile in physical education class. After resting for one hour, her heart rate was 𝟔𝟎 beats per minute. If

her heart rate decreased by 𝟐𝟓 while she rested, what was her heart rate immediately after she ran the mile?

𝒙 − 𝟐𝟓 𝒙 = 𝟔𝟎, 𝟑

𝟓 𝒙 = 𝟔𝟎, 𝒙 = 𝟏𝟎𝟎 beats per minute

Scaffolding:

For #3, show the different approaches that student might have used and discuss which approach is most efficient. An efficient approach simplifies the work needed for a multi-‐step problem such as #5.

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