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Cardboard Adding Machine

Here's something for the junior readers. Before people had computers, children used to play with, and invent, all kinds of games. Once I made an adding machine out of a cornflakes packet. The idea comes from a BBC children's television program called Blue Peter. Below you will find instructions on how to make one.

What you will need:

  • 1 box (for example: use an empty cornflakes packet)
  • 9 toothpicks (you could also use something like tent pegs)
  • 36 drop down cards

First you will need to make the drop down cards. Each card must have two peg support holes and seven escape slits cut into it, as shown in picture below. In the picture, the peg support holes appear at positions: 2 and 7. Two plus seven equals nine, so you need to write the answer 9 in centre of the card. You will have to work out the support hole positions and the correct answers for each individual card. The holes and slits must be positioned accurately or they won't line up properly. The easiest way to do this is to use a template.

         Drop Down Card Drop Down Card

Adding Machine
Adding Machine

The next thing to do is make the adding machine. Cut out a rectangular area from the front of the box, as shown in the picture on the right. This will be the card dispenser. Next you need to make nine peg holes in both the front and in the back of the box. Make sure that the peg holes are positioned accurately, so that they will line up with the holes in the drop down cards. Then, on the front of the box, number the holes 1 to 9.

Once you have made all the parts, you can assemble your adding machine. To do this: you need to line up the all cards and position them inside the box. The cards need to be supported by the pegs, by placing them through the holes. Now the adding machine is ready to be used. To add two numbers together, just remove two pegs. The answer should drop down into the card dispenser below.

You could vary the design by using more or less numbers. The one I made only used the numbers from 1 to 6. You could also create a different machine by using a different set of cards.