Estimate Engine Poster The Estimate Engine
Building 2-Digit × 1-Digit Products
1
Round the Big Factor
Find the 2-digit number. Round it to the nearest ten .
48
50
2
Keep the Small Factor
The 1-digit number stays exactly the same . Don't touch it!
× 7
× 7
3
Multiply the Basic Fact
Multiply non-zero digits, then attach the zero .
50 × 7 = 350
5 × 7 = 35... plus the zero!
Toolbox Example: 62 × 4
Actual
62 × 4
Estimate
60 × 4 = 240
"Estimation is like a blueprint—it gives you a plan before you build the final answer!"
Product Estimates Slides Mathematics Workshop
ESTIMATING
PRODUCTS
2-Digit × 1-Digit Rounding Strategy
Work in Progress ● Estimate First ● Round to Ten ● Build it Right ● Work in Progress ● Estimate First ● Round to Ten ● Build it Right ●
Why Estimate?
"Estimation is like checking the blueprint before you start building the house!"
Rounding Refresh
Round UP
If the ones digit is 5, 6, 7, 8, or 9...
37 → 40
Round DOWN
If the ones digit is 0, 1, 2, 3, or 4...
32 → 30
THE ESTIMATE ENGINE
1
Round Factor 1
Find the 2-digit number and round to the nearest ten.
2
Keep Factor 2
Leave the 1-digit number exactly as it is.
3
Multiply Facts
Multiply the basic fact and tack on the zero!
EXAMPLE #1
73 × 6 = ?
70
Rounded
×
6
Same
=
420
The Estimate!
7 × 6 = 42... plus 0 = 420
The "Up" Challenge
29 × 8 = ?
30
Rounded Up
×
8
=
240
29 is close to 30. 30 × 8 is much easier!
YOUR TURN!
Grab your whiteboards and estimate these products:
A
54 × 3
B
87 × 5
Blueprint Estimates Worksheet Blueprint Estimates
Product Estimation Site
Inspector Name:
Date:
Section 1: Rounding to the Nearest Ten
42 ___
78 ___
15 ___
94 ___
Section 2: Estimating Products
Actual Problem
Round & Multiply
Estimated Product
1. 37 × 4
____ × 4 =
=
2. 62 × 7
____ × 7 =
=
3. 23 × 9
____ × 9 =
=
4. 85 × 2
____ × 2 =
=
5. 49 × 5
____ × 5 =
=
Field Challenge
A construction crew needs to deliver 68 bags of concrete to 6 different sites . About how many bags do they need in total?
My Estimate: ____________________ bags
Quality Checked by Lenny Ed. Unit 4: Multiplication Estimates
Blueprint Estimates Answer Key Answer Key
Blueprint Estimates Verification
Teacher Resource
Section 1: Rounding to the Nearest Ten
42 40
78 80
15 20
94 90
Section 2: Estimating Products
37 × 4
40 × 4 =
160
62 × 7
60 × 7 =
420
23 × 9
20 × 9 =
180
85 × 2
90 × 2 =
180
49 × 5
50 × 5 =
250
Field Challenge Solution
Rounding: 68 rounds to 70
Equation: 70 × 6
Basic Fact: 7 × 6 = 42
Final Estimate: 420 bags
Estimate Engine Teacher Guide Estimate Engine
Teacher Instruction Guide
Learning Objective
Students will estimate products of 2-digit by 1-digit multiplication by rounding to the nearest ten and using basic facts with zeros.
Lesson Flow
05m
The Blueprint (Hook): Introduce estimation as a planning tool for construction projects.
15m
The Engine (Modeling): Use Slides to show Step 1 (Round Factor 1), Step 2 (Keep Factor 2), Step 3 (Basic Fact).
10m
Guided Inspection: Practice with whiteboards using "Your Turn" slides. Focus on not rounding the 1-digit factor.
20m
Field Work (Practice): Students complete the "Blueprint Estimates Worksheet" independently.
Common Pitfalls
Rounding the 1-digit factor (e.g., rounding 4 to 10 or 0).
Forgetting to attach the zero to the final product.
Rounding to the wrong place value.
Differentiation
Scaffold
Use a "Rounding Hill" visual aid and a multiplication chart for basic facts.
Extend
Ask students if the exact product will be higher or lower than the estimate and why.
