A Clock (Modular) Arithmetic Calculator
Here is a calculator for doing arithmetic (adding, subtracting, and multiplying)
whole numbers on a clock with a given number of hours. If this doesn't
make any sense to you, here's an explanation of what clock
arithmetic is, with an interactive clock that shows the different names
for a number on a clock in another way. Follow this link for another calculator
for renaming numbers on a clock.
Instructions
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Choose the operation you want (+, -, or x) by holding down the button with
the pull-down menu, and releasing on the one you want.
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Type the first number you want to calculate with in the first box.
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Type the second number you want to calculate with in the second box.
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Type the number of hours on the clock you want to use in the third box
(after "mod").
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Click the "=" button to get the smallest nonnegative "name" for the result
of the operation on the clock.
Problems? Got an "E"?
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Problems? Got an "E"?
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All numbers must be whole numbers. Except for the modulus, they can be
positive, negative, or 0.
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The number of hours on the clock (modulus) must be a whole number at least
2.
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If you type in a number bigger than the box, it will turn to an "E" (for
Error) because this computer program can't handle numbers above a certain
size.
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You have to click "=" or hit the return key after typing for the program
to calculate anything.
Technical Comments
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The notation is not quite standard; the "mod m" part should come at the
end of the sentence, not in the middle. And you should use the congruent
symbol (3 horizontal bars) instead of the = sign.
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Division is often impossible in modular arithmetic.
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This program uses the built-in java mod (%) operator. Because of limitations
on the size of integers in java, this applet can't handle very big numbers.
Original Web Site by Susan Addington