Course: 7th Grade Math
DETAIL LESSON PLAN
Student Objective
7.RP.3
Use proportional relationships to solve multistep ratio and percent problems.
Lesson
Lesson 7.2.2 – Replacement Lesson
Setting Up and Solving Proportions
Homework
Proportion word problems (7 questions).
Bellwork
Teacher selected
Prior Knowledge
 Review bellwork and homework.
 Yesterday, we learned about ratios. A ratio is the comparison of two quantities by division.
We also, learned about proportions. A proportion states that 2 ratios are equal. We learned that you can use cross
multiplication to determine if 2 ratios are equal to each other. We also solved proportions that had a variable.
Anticipatory Set
 Today… we are going to continue our study of proportions, but we will focus on setting up a proportion from scratch
given particular situation.

Show PowerPoint: “Body Types”

Why learn?
Proportions can be used to find missing numbers in a real world math problem. Later on in the third nine weeks we will see
how proportions can be used to solve problems involving scale models and similar figures. Engineers use scale models to
build high tech aircraft. If two figures are similar (same shape, but different size), a proportion can be used to find a missing
side length on one of the shapes.
Teacher Input
 Review bellwork and homework.
 Pass out notes
 Show PowerPoint on Body Types to introduce today’s lesson on proportions.
 Why learn? Show circle map.
 Define a Proportion. Review how to determine if two ratios form a proportion (cross multiply).
 Work 1 guided practice problem with students.
 Review how to solve a proportion if a variable is involved.
 Work 1 guided practice problem with students.
 Discuss how to set up a proportion for a given situation using a flow map.
 Students must remember that when setting up a proportion you must put like units across from each other.
 Work guided practice problems involving goggles and football.
 Students will work 2 you try problems (independently).



Classwork: Proportion Word Problem WS (6 problems) Think, Pair, Share
Extra Practice: Ratio and Proportion extra practice problems
Homework: Proportion Word Problem WS (7 problems)
Assessment
Observation and questioning.
Closure
1. When setting up a proportion, it is important that the same units are _________? across from each other.
Inches across from ______? inches
Dollars across form ____? dollars
Pounds across from ____? pounds
2. Once you set up the proportion, what do you do? cross multiply
Once you cross multiply your are left with a 1 step __________to solve. equation
Student Notes
Setting Up Proportions
Proportions – What are they? How do you set them up? When will we use them?
Definition:
States that 2 ratios are equal.
=
To determine if 2 ratios
form a proportion:
=
To solve proportions with
a variable:
=
cross multiply
Setting up a proportion:
Put the like units across from
each other…
cross multiply
Proportions
Similar Figures:
Important to Remember
There is not just one correct way to set up a proportion.
The key (
) is to make sure that you put the “like units” across from each other.
Swimming goggles are 12 for $84.36.
At this rate, how much would it cost for 17 goggles?
Ratio 1
1st way:
. Ratio 2
2nd way:
Answer: $119.51
Answer: $119.51
Setting up and solving proportions.
When setting up a proportion, the key is to make sure that you put the “like units” across from
each other.
inches
miles
feet
inches
miles
feet
Step 1
Step 2
Take the information
in the first sentence
and make that your
first ratio.
Take the information
in the second sentence
and set the second
ratio up to where the
“like units” are across
from each other.
Step 3
Cross multiply.
Step 3
Solve the one-step
equation.
Write a proportion for the situation. Then solve.
A football player runs 25 yards in 2.5 seconds. How many seconds should it take
the same football player to run 100 yards?
=
25x = 250
You Try!
1. Jim’s heartbeat is 142 beats per 2 minutes. Which proportion would give
Jim’s heartbeat in 8 minutes?
A)
C)
B)
D)
Both B and C
2. Write a proportion for the situation. Then solve.
3 ounces for $1.65; 5 ounces for “x” dollars.
x = 10
Name__________________________ Date___________ Period: ______
Proportion Word Problems
Answer each question using proportions. Round your answer to the nearest whole number.
1) If you can buy one can of pineapple chunks
for $2, then how many can you buy with $10?
2) One jar of crushed ginger cost $2. How
many jars can you buy for $4?
3) Ming was planning a trip to West Samoa.
Before going, she did some research and
learned that the exchange rate is 6 Tala
for $2. How many Tala would she get if
she exchanged $6?
4) Jasmine bought 32 kiwi fruit for $16. If
Jasmine has $4, how many kiwi can she
buy?
5) Shawna’s original rectangle was 24
inches wide and 12 inches tall. If she
reduced the size of the rectangle to 2
inches tall, then what is the new width?
6) If you can buy four bulbs of elephant garlic
for $8, then how many can you buy with
$32?
Name__________________________ Date__________
Period: ____
Simplify each RATIO. Write your answer 3 different ways.
1)
2) 4 : 8
Cross multiply to determine if each set of ratios form a proportion.
3)
4)
Yes or No
5)
Yes or No
Yes or No
Solve each proportion.
6)
=
7)
=
8)
=
9)
=
10)
=
11)
=
12)
Write a proportion for the following situation. Then solve.
20 ounces at $7; 17 ounces at x dollars
Name:_____________________
Date:_____________
Period:_______
Set up a proportion for each situation. Then solve.
No credit if not solved using proportions!
1) 3 subscriptions to a particular magazine is $63.
How much would 28 subscriptions cost?
2) 4 runs in 3 innings; x runs in 9 innings.
3) 3 miles in 2.8 minutes; 33.3 miles in x minutes.
4) 20 pounds for $27.50;
12 pounds for x dollars.
5) You estimate that you can do 12 math
6) Ty scores 75 points in 6 games. At this
problems in 45 minutes. How long should it
take to work 20 problems.
7) A student types 120 words in 3 minutes.
How many minutes does it take for the
student to type 200 words?
rate, how many points did Ty score in 4
games?