Freebie Friday: Magic Number Cards

You will love this freebie! Sometimes a lesson ends a little earlier than expected and teachers need to reach into their toolkit to find something to occupy the kids for a few minutes. This is one of my favorites...Magic Number Cards! Okay, so it's not really magic, but your students will think it is! Your students will be amazed when they learn their teacher has magical powers.

This simple math trick uses the binary number system. Don't worry, I'm not going to get into what a binary number system is and you certainly don't need to know it to dazzle your students with this trick. However, if you're curious, you should look it up--it's very cool!

Anyway, this is how it works:

• MS. MAI: Johnny, I can read your brain! Pick a secret number from 1 to 63. DO NOT tell me what it is. Then, write it on this little whiteboard without letting me see it. (This ensures that the student won't change his answer.)
• JOHNNY: Okay. (writes down the number)
• MS. MAI: Now, look at these 6 cards. Give me every card that has your secret number on it. If the card does not have your secret number on it, I do not want it. 

• JOHNNY: Here you go Ms. Mai. Each of these cards have my secret number on it.

 

• MS. MAI: Hmmmmm...I'm reading your brain...(add the first number in the upper left-hand corner on each card: 2 + 4 + 16 = 22). Your secret number is...22!
• JOHNNY: (shows the number 22, written on his board to the class) How did you do that??
• MS. MAI: Magic.

I hope you enjoy this freebie! Thanks for hosting "Freebie Friday" Teaching Blog Addict!