Skip to main content

X-RAY EYES! MULTIPLICATION MAGIC

Hi All,

This is not a big time math lesson, but kids love a good magic trick they can do, so here it is. This one uses the sevens times table and is a snap to learn.

*Tell students that if they roll a pair of dice you will be able to tell them the total of all the top numbers and bottom numbers (without looking at the bottom) because of your "x-ray eyes."

*The secret is that on any die, the top number and the bottom number always equal 7. Roll two dice and the total is going to be 14. Roll three dice and it will be 21. Four dice will be 28, and so on through the 7 times table.

*Begin with students rolling two dice, then three, then four, and let them use as many as you have available. See if they can figure out the trick.

*Once they figure it out (or you reveal it), they can practice and then take their "multiplying magic show" on the road and share it with others.

Simple, but fun.  Oh, and keep the dice handy, on Thursday we'll get "Deeper with Dice."

All the best,
Bob

Adapted from Mathemagic by Raymond Blum (Sterling, 1991)

Comments

Popular posts from this blog

What Does Not Belong?

 Hi All,   "What Does Not Belong" is such a great little concept and can be applied to so many different areas of math as well as other content areas. Great little game when you are waiting, like for buses to be called or for the day to begin. Also a great game for long car or bus rides where if there are no written numbers or pictures you really have to do the mental math. Present a group of numbers. Start with maybe six. Say, 10     56     17     122     4     98 Ask the players to identify which number does not belong and have them explain why. We want players to look at the characteristics of the numbers and compare them to try to find the selection criteria or "rule" so they can determine which does not belong. For example, we have a mix of 1, 2, and 3 digit numbers, so it's not the "rule" is not the number of digits. We have five even numbers and only one odd number. That's it! 17 does not belong,...

Piaget Would be Proud! Assessment, Mental Math, Manipulatives, Thinking, Missing Addends, and Kumquats!

 Hi All, This is a super simple, but very revealing activity and so works as a good assessment. Fantastic for Pre-K, Kindergarten, and Grade 1. Try it out and see what you learn about your students. Display a small number of objects in your open hands. Here we have 4 kumquats. (Because I have a kumquat tree in my yard. Any small manipulative will do.) Put your hands behind your back. Close one hand and bring both hands back out in front of you to display 2 kumquats visible in one hand and a closed hand with the rest of them. Remind students that you started with 4 and there are still 4 all together. Ask students, what is in the closed hand. Ask how they know this. Then reveal and discuss. Try another one. Show the 4 objects again, 2 in each hand. Put your hands behind your back and redistribute with 1 object in one hand and 3 objects in the other. Bring your hands to the front and ask how many are in your closed hand. Ask how they know this.  Then reveal and discuss.   Yo...

Calculator Caller!

Hi All, I had a colleague I taught with for years. She was a passionate second grade teacher with a lot of solid experience. A parent once asked her, "What is the most important thing you can teach a child?" I was thinking that's a tough question. Maybe, to treat others like you would treat yourself? Her immediate reply was, "Place value." Ha, ha! She was a real math maven! Place value is important though! Here's one fun partner activity that gives kids practice with calculators (which they need in standardized tests as well as real life), place value, number recognition, and number words. It's motivating because most kids love to get their hands on calculators and as teachers and parents we're usually telling them, "No calculators!"   1. Each player gets a calculator and a recording sheet. The lead player decides on a number, inputs it into his calculator, writes it down on the record sheet, says it aloud, but does not let his partner se...