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Dr. K
Home
About
Biography
PhD
University of Michigan
Family
My Dog, Yeti
with Famous Mathematicians
Museum of Math (MoMATH)
StreetSquash Harlem
US Army Service
Bicycles and Motorcycle
NYC Deli Cats
Tricks
Number Guessing
Guess Your Number
Honest Liar
2-Digit Mind Reader
Cubic Root Calculation
Check Digits
Check Digit Algorithms
Check Digit Anchor Charts
Check Digit Worksheets
Check Digit Calculator
8-Digit Barcode
12-Digit Barcode (UPC)
13-Digit Barcode (ISBN)
14-Digit Barcode
15-Digit Credit Card (American Express)
16-Digit Credit Card (VISA & MasterCard)
17-Digit VIN
18-Digit Barcode
Calculator Tricks
3-peat 777
6-peat 777,777
9-peat 777,777,777
Devil's 666
3-Digit Repeat 123 123
4-Digit Repeat 1234 1234
5-Digit Repeat 12345 12345
Guess Your Birthday
6 Times Even
Pretend Mental Math
Addition 18
Calendar Math Tricks
Ancient Calculators
Multiplication By Lines
Roman Multiplication
Lattice Multiplication
Napier Bones Multiplication
Slide Rules
Abacuses
Division By Dots
Binary Holes Sorting
Magic Card Tricks
4th Card
1/7
Four Sevens
2 More & Get You To 20
Math Talks
Full Precision Calculator
Puzzles
Wordle, Nerdle, and More
SIMP
Transum Puzzles
Grid Puzzles
Calcudoku
Skyscrappers
Kubok
Kakuro
Capsules
Products
Different Strokes
Thermometers
Arrows
Borderlands
Assembly Puzzles
Wooden Egg
Moses' Snake Cube
6-Piece Ball
Soma Cube
Sliding Puzzles
15 Puzzle
Setting Sun Puzzle
Colors Disk Puzzle
Ball Colors Puzzle
Arranging Puzzles
Cruiser 4-Piece Wooden
Hercules Puzzle
Math Blanks Puzzles
Magic Triangle
Bar Model Fractions
Pyramid Addition
Not Too Close
Hexa-Trex
Visual Logic
Other Math Puzzles
Kinesthetic Puzzles
String Handcuffs
Art Puzzles
Mondrian Math
Verbal Logic Puzzles
Riddles
Emperor's Proposition
Alliteration Multiplication Word Problems
Counting Puzzles
How Many Triangles?
How Many Squares?
How Many Rectangles?
Code Breaking Puzzles
Mastermind
Optical Illusion Puzzles
Games
2-Player Games
Connect 4
Cat and Mouse
NIM - Sea Shells
NIM - Matchsticks Pyramid
Intransitive Dice
Make 15
Multi-Player Games
Rummikub
Blokus
Pit
SET
On The Dot
Rubik's Cubes
Layer By Layer Method
CFOP Method
Cubing Culture
Mosaics
Patterns
Calendar Cubes
Fruit Cubes
Mirror Cubes
Giant Cubes
Void Cubes
Pyramix Cubes
Megaminx Cubes
Egg Cubes
Ivy Cubes
Skewb Cubes
Oblique Prism Cubes
Gear Cubes
NxN Algorithms
Robots
Other Cubes
Math Everywhere
Math on TV
Math In Books
Math Augmented Reality
Invisible Math
Betting Odds in Sports
NFL QB Passer Rating
Math Memes
Math Fails
Tonic Water Calories
Gym Membership Plans
Bloomberg Spending
3 + Dozen = 15
Bitcoin
Dr. K
Home
About
Biography
PhD
University of Michigan
Family
My Dog, Yeti
with Famous Mathematicians
Museum of Math (MoMATH)
StreetSquash Harlem
US Army Service
Bicycles and Motorcycle
NYC Deli Cats
Tricks
Number Guessing
Guess Your Number
Honest Liar
2-Digit Mind Reader
Cubic Root Calculation
Check Digits
Check Digit Algorithms
Check Digit Anchor Charts
Check Digit Worksheets
Check Digit Calculator
8-Digit Barcode
12-Digit Barcode (UPC)
13-Digit Barcode (ISBN)
14-Digit Barcode
15-Digit Credit Card (American Express)
16-Digit Credit Card (VISA & MasterCard)
17-Digit VIN
18-Digit Barcode
Calculator Tricks
3-peat 777
6-peat 777,777
9-peat 777,777,777
Devil's 666
3-Digit Repeat 123 123
4-Digit Repeat 1234 1234
5-Digit Repeat 12345 12345
Guess Your Birthday
6 Times Even
Pretend Mental Math
Addition 18
Calendar Math Tricks
Ancient Calculators
Multiplication By Lines
Roman Multiplication
Lattice Multiplication
Napier Bones Multiplication
Slide Rules
Abacuses
Division By Dots
Binary Holes Sorting
Magic Card Tricks
4th Card
1/7
Four Sevens
2 More & Get You To 20
Math Talks
Full Precision Calculator
Puzzles
Wordle, Nerdle, and More
SIMP
Transum Puzzles
Grid Puzzles
Calcudoku
Skyscrappers
Kubok
Kakuro
Capsules
Products
Different Strokes
Thermometers
Arrows
Borderlands
Assembly Puzzles
Wooden Egg
Moses' Snake Cube
6-Piece Ball
Soma Cube
Sliding Puzzles
15 Puzzle
Setting Sun Puzzle
Colors Disk Puzzle
Ball Colors Puzzle
Arranging Puzzles
Cruiser 4-Piece Wooden
Hercules Puzzle
Math Blanks Puzzles
Magic Triangle
Bar Model Fractions
Pyramid Addition
Not Too Close
Hexa-Trex
Visual Logic
Other Math Puzzles
Kinesthetic Puzzles
String Handcuffs
Art Puzzles
Mondrian Math
Verbal Logic Puzzles
Riddles
Emperor's Proposition
Alliteration Multiplication Word Problems
Counting Puzzles
How Many Triangles?
How Many Squares?
How Many Rectangles?
Code Breaking Puzzles
Mastermind
Optical Illusion Puzzles
Games
2-Player Games
Connect 4
Cat and Mouse
NIM - Sea Shells
NIM - Matchsticks Pyramid
Intransitive Dice
Make 15
Multi-Player Games
Rummikub
Blokus
Pit
SET
On The Dot
Rubik's Cubes
Layer By Layer Method
CFOP Method
Cubing Culture
Mosaics
Patterns
Calendar Cubes
Fruit Cubes
Mirror Cubes
Giant Cubes
Void Cubes
Pyramix Cubes
Megaminx Cubes
Egg Cubes
Ivy Cubes
Skewb Cubes
Oblique Prism Cubes
Gear Cubes
NxN Algorithms
Robots
Other Cubes
Math Everywhere
Math on TV
Math In Books
Math Augmented Reality
Invisible Math
Betting Odds in Sports
NFL QB Passer Rating
Math Memes
Math Fails
Tonic Water Calories
Gym Membership Plans
Bloomberg Spending
3 + Dozen = 15
Bitcoin
More
Home
About
Biography
PhD
University of Michigan
Family
My Dog, Yeti
with Famous Mathematicians
Museum of Math (MoMATH)
StreetSquash Harlem
US Army Service
Bicycles and Motorcycle
NYC Deli Cats
Tricks
Number Guessing
Guess Your Number
Honest Liar
2-Digit Mind Reader
Cubic Root Calculation
Check Digits
Check Digit Algorithms
Check Digit Anchor Charts
Check Digit Worksheets
Check Digit Calculator
8-Digit Barcode
12-Digit Barcode (UPC)
13-Digit Barcode (ISBN)
14-Digit Barcode
15-Digit Credit Card (American Express)
16-Digit Credit Card (VISA & MasterCard)
17-Digit VIN
18-Digit Barcode
Calculator Tricks
3-peat 777
6-peat 777,777
9-peat 777,777,777
Devil's 666
3-Digit Repeat 123 123
4-Digit Repeat 1234 1234
5-Digit Repeat 12345 12345
Guess Your Birthday
6 Times Even
Pretend Mental Math
Addition 18
Calendar Math Tricks
Ancient Calculators
Multiplication By Lines
Roman Multiplication
Lattice Multiplication
Napier Bones Multiplication
Slide Rules
Abacuses
Division By Dots
Binary Holes Sorting
Magic Card Tricks
4th Card
1/7
Four Sevens
2 More & Get You To 20
Math Talks
Full Precision Calculator
Puzzles
Wordle, Nerdle, and More
SIMP
Transum Puzzles
Grid Puzzles
Calcudoku
Skyscrappers
Kubok
Kakuro
Capsules
Products
Different Strokes
Thermometers
Arrows
Borderlands
Assembly Puzzles
Wooden Egg
Moses' Snake Cube
6-Piece Ball
Soma Cube
Sliding Puzzles
15 Puzzle
Setting Sun Puzzle
Colors Disk Puzzle
Ball Colors Puzzle
Arranging Puzzles
Cruiser 4-Piece Wooden
Hercules Puzzle
Math Blanks Puzzles
Magic Triangle
Bar Model Fractions
Pyramid Addition
Not Too Close
Hexa-Trex
Visual Logic
Other Math Puzzles
Kinesthetic Puzzles
String Handcuffs
Art Puzzles
Mondrian Math
Verbal Logic Puzzles
Riddles
Emperor's Proposition
Alliteration Multiplication Word Problems
Counting Puzzles
How Many Triangles?
How Many Squares?
How Many Rectangles?
Code Breaking Puzzles
Mastermind
Optical Illusion Puzzles
Games
2-Player Games
Connect 4
Cat and Mouse
NIM - Sea Shells
NIM - Matchsticks Pyramid
Intransitive Dice
Make 15
Multi-Player Games
Rummikub
Blokus
Pit
SET
On The Dot
Rubik's Cubes
Layer By Layer Method
CFOP Method
Cubing Culture
Mosaics
Patterns
Calendar Cubes
Fruit Cubes
Mirror Cubes
Giant Cubes
Void Cubes
Pyramix Cubes
Megaminx Cubes
Egg Cubes
Ivy Cubes
Skewb Cubes
Oblique Prism Cubes
Gear Cubes
NxN Algorithms
Robots
Other Cubes
Math Everywhere
Math on TV
Math In Books
Math Augmented Reality
Invisible Math
Betting Odds in Sports
NFL QB Passer Rating
Math Memes
Math Fails
Tonic Water Calories
Gym Membership Plans
Bloomberg Spending
3 + Dozen = 15
Bitcoin
How Many Triangles?
Scroll Down For Answer and Explanation
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