Number Devil Activities: The Fifth Night

In the fifth chapter of The Number Devil, Robert finds himself in the desert amidst coconuts and triangle numbers.

Activity One:

Supplies:

• Triangle numbers worksheet
• Answer key

The Number Devil challenges Robert to, "Pick a number, any number, and I can show it to be the sum of either two or three triangle numbers."  Use the triangle number worksheet  to see if you are up to the challenge.

Activity Two:

Supplies:

• Mathematicians are People, Too

Learn about Gauss.  Legend has it that as a boy, the famous mathematician Karl Friedrich Gauss showed the pattern of adding numbers in a sequence together when confronted with a challenge to add all the numbers from 1 to 100 together.  Instead of adding 2 to 1 and then adding 3 to the answer and 4 to that answer on so on, he grouped the numbers in pairs:

1+100=101

2+99=101

50+51=101

Seeing the pattern, Gauss jumped to the answer by multiplying 101 x 50 discovering the one hundredth triangle number of 5,050.

Mathematicians are People, Too shares a delightful story of Karl Friedrich Gauss.  Read and discuss the story.

Activity Three:

Supplies:

• Deck of cards with the numbers from 1 to 100
• Slapjack rules

Play Triangle Number Slapjack with 1 to 3 friends.  Use a deck of cards with numbers between 1 and 100.  Instead of slapping "jacks", the players slap triangle numbers (1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91) to win the pile.  If needed, review the rules for slapjack.

Snack Idea:

Make a tasty coconut lime smoothie.  Fill a blender with ice, 1 can of coconut milk, and limeade.  Blend until smooth.

Challenge Question:

Only two numbers between 1 and 100 hold the distinction of being both square numbers and triangle numbers.  The first is the number 1.  What is the other number that is both a triangle number and a square number?  Click here for the answer.

More Number Devil Activities

Do you have an idea for the Fifth Night of The Number Devil?  Share your ideas with us below.