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How to Use a Wizard Slide Adder

A slide adder is a mechanical precursor of the calculator, allowing users to perform mathematical operations. Produced in West Germany in the 1950s, the Wizard calculating machine is an example of a slide adder. The metal faceplate of the Wizard features eight slots, with the numbers one through nine printed along the slide of each slot. Behind each slot is a notched slider. As with similar slide adders, you operate the Wizard by manipulating the mechanical sliders behind the metal faceplate using a stylus. A window above each slot displays each digit of the answer.

Instructions

- 1
  Enter the first digit. Place the stylus in the slider notch corresponding to the ones unit of your first number and move that notch to the bottom of the rightmost slot in the Wizard's faceplate. Look into the small window above the column; the correct number should appear there. For example, if you are adding 15 and 28, your first digit is 5.
- 2
  Input the next digit into the tens column -- the second slot from the right -- in the same way you entered the first digit. In the 15 + 28 example, you would place the point of the stylus into the notch next to the number 1 and move this notch to the bottom of the slot. A "1" should appear in the window above the slot.
- 3
  Input the other digits of your first number (if any) in the same way that you input the first two digits.
- 4
  Input your second number in the same way you input the first number, starting with the ones digit. If the total of the two numbers' units is greater than 9, you will need to carry the 1. You will see that the notch in the slider is now red rather than white. Note that the top of the slot is shaped like a shepherds' crook. Place your stylus in the notch next to the unit you want to add (8 in the case of 15 + 28), move it all the way to the top of the slot in the faceplate and around the shepherds' crook-shaped hook at the top.
- 5
  Input the other digits of your second number in the same way. Remember to carry the tens digit when indicated by a red notch. Your total will appear in the windows above the slots.

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