Dice towers (simple version) – Maths Magic

dicetower  What’s the effect?

A spectator stacks up a tower of dice whilst the magician’s back is turned away. The magician turns around and immediately names a number out loud. This number is the total of all the hidden faces (i.e. the top and bottom faces except for the very top one).

What you need:

  • Dice (I usually use 4 dice). The bigger the dice the better as it makes it very visual.

What’s the method?

The principle behind the magic is that opposite faces of a dice total 7. eg 1&6; 2&5; 3&4.

For a tower you then know the total sum of ALL the top and bottom faces will equal 7 times the number of dice in the tower. So for the example in the photo the total sum is 28.

To calculate the total sum of the hidden faces you need to do a very simple calculation when you turn around to face the audience. First look at the number on the very top and then subtract that from the number you obtained earlier. In the photo example you have to do 28-6=22.

Walking through a postcard – Experiment

What’s the effect?

You cut a hole in an A5 piece of paper large enough for someone to climb through. (This is a good follow on activity from the “Coin through an impossible hole“.)

You will need:

  • A piece of A5 paper
  • Scissors

walkthru

What’s the method?

Start by folding the A5 piece of paper in half lengthwise (see photo 1).

Now make cuts in the piece of paper starting from the folded edge and stopping 1cm from the opposite edge. You want the cuts to be spaced by about 1cm. The result will look like a paper comb (see photo 2).

Now turn the piece of paper around and make cuts from the opposite side. These cuts are made in between the cuts you’ve previously made. Again stop cutting 1 cm from the edge. You will now have created a zig zag shape as in (photo 3).

The next step (also shown in photo 3) is to carefully cut along the folds you made at the start. However, you want to leave the folds on the left and right edges intact. When you’ve completed these cuts and carefully unfolded your creation it should look like photo 4.

By carefully pulling the paper apart you will have created a large hole in the middle (see photo 5). You can then climb through it or have a volunteer climb through. You need to watch the paper doesn’t catch on clothing or it will tear easily.

This is a good activity when teaching about perimeter and area.

Coin through an impossible hole – Experiment

What’s the effect?

A 2 pence coin is pushed through the hole made by a 1 pence coin.

You will need:

  • A piece of paper
  • 1x 2p coin and 1x 1p coin
  • Scissors
  • Paper/pen

Image

What’s the method?

The series of photos above outlines how to do this. Start by drawing around the 1p coin with the pen or pencil. Then carefully cut out the hole with the scissors (see photo 2).

The challenge is then to push the 2p coin through the 1p coin’s hole. Which would seem impossible as the hole is clearly too small (as can be seen in photo 3).

To achieve the impossible… fold the paper in half, with the fold going directly across the hole’s diameter. Then insert the 2p coin into the paper (see photo 4).

The hole still seems to small but if you pinch the paper and fold the paper in such a way so that the curved hole begins to get straightened out (see photo 5) eventually you’ll reach a point where the 2p drops through the hole.

This is a good way of introducing the idea of circumference and diameter.