Ratio Mastermind Teacher Guide Ratio Bar Model Mastery
Teacher Facilitation Guide • 7th Grade Mathematics
Duration
45 Minutes
Learning Objective
Students will use bar models (tape diagrams) to visualize and solve ratio problems by identifying the value of a single unit (the unitary method).
Materials Needed
Ratio Blueprint Slides
Ratio Lab Worksheet (or individual whiteboards)
Dry erase markers / Pencil
Video: "Ratio and Proportion"
Instructional Sequence
5 MIN
The Hook: Visual Comparison
Draw a bar model representing a 1:5 ratio on the board. Do not provide numbers yet. Ask: "If the small box represents 'sugar' and the big boxes represent 'water', what can we say about this recipe?"
15 MIN
Video Part 1: Lemonade Modeling
Play the Lemonade Section (0:09–1:26) . Pause at 0:30 .
Discussion Prompt:
"If the ratio is 1:5, which number represents the lemon juice and which represents the water? How do you know?"
Pause at 0:35 . Model labeling the 1 unit as "26L". Demonstrate finding the 5 units by multiplying 26 × 5.
15 MIN
Video Part 2: Ice Cream (Student Lead)
Play the Ice Cream Section (1:27–2:44) . Pause at 1:59 after the problem setup.
Task: Students draw the 1:7:3 bar model.
Key Check:
Ensure students label the 3 units (Strawberry) as 162. Watch for students who try to label the first box as 162.
5 MIN
Calculation & Verification
Students solve for "1 unit" (162 ÷ 3 = 54). Then find the total. Ask: "What operation finds the 'altogether' amount?" Before playing the final 14 seconds of the video, have students predict the total.
5 MIN
Peer Check
Students trade work. They check two things: 1) Is the model drawn to scale (correct number of boxes)? 2) Is the label '162' attached to the correct section?
Watch Out For...
Partial vs. Total: Students may forget to add the original lemon juice (26L) back into the water amount when asked for the "total lemonade".The "Divide by First" Error: In the ice cream problem, ensure students divide by 3 (the strawberry units) and not 11 (the total units) until they find the value of one unit. Ratio Blueprint Slides 7th Grade Math
RATIO
BLUEPRINTS
Visualizing relationships and solving multi-step problems using the unitary method.
Model • Build • Solve
Mission Objective
I can use bar models to visualize ratio problems and find the value of one unit to solve complex math challenges.
Identify Ratios
Draw Bar Models
Master Unitary Method
The Hook
Look at this model. What story does it tell?
?
The Ratio
1 : 5
The Key Question
"If the yellow box is sugar and the blue boxes are water, how sweet is this drink?"
Part 1: The Lemonade Lab
MODELING PHASE
WATCH & OBSERVE
Embedded media
The Facts
Ratio 1:5
26L Lemon Juice
Problem:
How much water is needed? How much lemonade total?
PAUSE & THINK (Video at 0:30)
If the ratio is 1:5...
Which number represents the juice?
1
The 1st Part
5
The 2nd Part
Hint: Look at the order of the words in the problem!
The Unitary Method
1
Find 1 Unit
The problem says 26L is the juice. Juice is the "1" in 1:5.
1 Unit = 26 L
2
Find the Rest
Water is 5 units. If 1 box is 26, then 5 boxes are...
26
26 × 5 = 130
"If one unit is 26, five units is 26 five times."
Part 2: The Ice Cream Factory
YOUR TURN TO BUILD
1 : 7 : 3
The factory makes Chocolate, Vanilla, and Strawberry ice cream.
Chocolate: 1 Vanilla: 7 Strawberry: 3
The Clue
162 tubs of strawberry
This 162 represents the STRAWBERRY part of the ratio.
Ready your whiteboards!
The Task:
Draw a bar model for 1 : 7 : 3
Label the Strawberry section as 162
Find the value of ONE UNIT
Calculate the TOTAL production
Build Phase
WATCH UNTIL 1:59 AND PAUSE
Embedded media
Ratio Blueprint Recording Sheet Ratio Blueprint Lab
Name:
Date:
Use this sheet to map out the ratios and calculations from today's challenge.
1 Phase 1: The Hook (Ratio 1:5)
Draw your 1:5 bar model here:
If the ratio represents sugar to water, describe the mixture:
2 Phase 2: The Lemonade Challenge
Input Data
Ratio 1:5 (Juice to Water)
Known: 26L Lemon Juice
Bar Model Diagram:
Calculations
Value of 1 Unit:
Litres of Water (5 Units):
TOTAL Lemonade produced:
3 Phase 3: The Ice Cream Factory (Ratio 1:7:3)
Chocolate
1
Vanilla
7
Strawberry
3
Known Data: 162 Tubs of Strawberry
Draw your multi-part bar model below
Unitary Method
Which part of the ratio represents 162 tubs?
Calculate the value of ONE UNIT:
Final Blueprint Data
Chocolate tubs:
Vanilla tubs:
TOTAL ALTOGETHER:
Reflect
"Why is it important to find the value of one unit before solving for the total?"
Ratio Blueprint Answer Key Teacher Answer Key
Ratio Blueprint Lab • 7th Grade Math
Reference Only
Phase 1: The Hook (1:5)
Expected Model:
(1 part sugar, 5 parts water)
Analysis:
Students should note that the mixture is very dilute or "mostly water". 5/6 of the total volume is water.
Phase 2: The Lemonade Challenge
Model & Labels:
26
26
26
26
26
26
Juice (1 unit)
Water (5 units)
Calculations:
Value of 1 Unit: 26 L
Water (26 × 5): 130 L
Total (26 + 130): 156 L
Phase 3: The Ice Cream Factory
Master Model (1:7:3)
Choc (1)
54
Vanilla (7)
54
54
54
54
54
54
54
Straw (3)
54
54
54
162
Calculated value of 1 unit: 162 ÷ 3 = 54
Unit Totals:
Chocolate: 54
Vanilla (54 × 7): 378
Strawberry: 162
Grand Total Altogether:
594 Tubs
Reflection Guide
Expected Student Response: "Finding the value of one unit allows us to calculate any part of the ratio or the total because all units in a bar model are equal in size. It's the 'building block' for the whole problem."
