This is a good magic math trick for kids who could use a little subtraction practice. It gives them an incentive to do subtraction because that is how the trick works. Good for Kids in 2nd to 3rd grades but older students like it too.
- Start with two dice. Have your subject roll the dice and then stack them one on top of the other. Now there are 3 numbers you cannot see:
o the bottom of the top dice
o the top of the bottom dice
o the bottom of the bottom dice
- Make it a point to let the person know that you cannot see those faces of the dice. Here is where the math magic comes in.
- Tell them you'll be able to tell them how much the three hidden faces add up to. In your head subtract the very top face of the two dice from 14. This is the number that the other three will add up to. For example, if the top number is 6, the other three will add up to (14-6 = 8) 8! Pretty Cool!
- You can do this with three dice also. Instead, just subtract the top number from 21.
Tips: Opposite faces of a dice add up to 7.