Decimal Dash Teacher Guide Decimal Dash
Teacher Facilitation Guide
Grade 5 • Math
Learning Objective
Students will practice rounding decimals to the nearest whole number to facilitate quick mental multiplication and estimation.
Materials Needed
Floor Tape / Number Line
0, 5, 10 Labels
Relay Flashcards
Whiteboards/Markers
"Decimal Dash" Slides
Exit Ticket
Pacing
Warm-up 5 min
Video/Discussion 10 min
Rounding Relay 15 min
Extension 5 min
1
Warm-up: Human Number Line
Use tape to create a number line on the floor with labels for 0, 5, and 10 .
"I'm going to call out a decimal. I want you to walk to where that number would be on the floor, then jump to the whole number it is closest to."
Examples: 7.8 (Jump to 8), 2.4 (Jump to 2), 4.5 (Jump to 5).
2
Video & Deep Dive
Watch the "Mixed Rounding" segment (4:26-5:08 ).
Discussion Questions:
Why does 7.5 round to 8, but 2.4 rounds down to 2?
What is the "Midpoint Rule"? (5 and up rounds up).
Why is it easier to multiply \(8 \times 2\) than \(7.5 \times 2.4\)?
3
The Rounding Relay
Split the class into teams of 3-4. Place the Relay Flashcards at a station across the room.
Player 1
Rounds first number
Player 2
Rounds second number
Player 3
Multiplies the products
Rotation: After each round, students shift roles so everyone practices each step.
E
Extension Challenge
Introduce three factors: \(2.1 \times 4.9 \times 3.2\). Teams must round all three and find the final estimated product.
Decimal Dash Slides Decimal Dash
Mastering Estimation in Motion
Grade 5 Math
Our Mission
I can round decimals to the nearest whole number to estimate products using mental math.
The Goal Quick Accuracy
The Tool The Rounding Rule
Warm-Up
Human Number Line
1
Listen for the decimal.
2
Find your spot on the floor line.
3
Jump to the nearest whole number!
Ready?
Try These:
Pro Rounding: Mixed Problems
4:26 - 5:08
Embedded media
Watch for the 7.5 → 8 jump!
The Rounding Relay
Teamwork makes the estimate work!
1
The First Rounder
Rounds the first decimal to a whole number.
2
The Second Rounder
Rounds the second decimal to a whole number.
3
The Multiplier
Multiplies both whole numbers for the final result.
Rotate roles after every problem!
Ultimate Challenge
2.1 × 4.9 × 3.2
Can your team round all 3 and multiply in 30 seconds?
Round 'Em
Dash 'Em
Done!
Decimal Dash Printables Floor Labels: Physical Number Line
Cut along the dotted lines and tape these to the floor 3-4 feet apart.
0
Start Point
5
The Midpoint
10
End Point
Decimal Dash: Relay Problem Cards
Hand one set to each team or place at the turnaround point.
Problem A
6.2 × 3.9
Round Round Multiply
Problem B
8.7 × 2.1
Round Round Multiply
Problem C
4.5 × 5.5
Round Round Multiply
Problem D
12.3 × 3.1
Round Round Multiply
Extreme Challenge Triple Threat
2.1 × 4.9 × 3.2
Round All Three • Final Estimate
Decimal Dash Exit Ticket Decimal Dash Exit Ticket
Show your rounding and multiplication speed!
Name:
Date:
Part 1: The Quick Jump
Round each decimal to the nearest whole number.
7.5
2.4
12.9
Part 2: Estimated Products
Estimate the product by rounding each number first. Show your rounded numbers!
4.8 × 6.1
×
=
9.5 × 3.2
×
=
The Big Question
Why do we round 7.5 to 8 instead of 7? Explain the rule.
