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How many combinations of the numbers 1 and 4 can there be using four digits?

In: Math and Arithmetic [Edit categories]

Answer:

Think of either using or not using the numbers 1 and 4 for each digit.

For example, let ____ ____ _____ ____ be the 4 digit number, now 1 can either go in to the first spot or 4 can. So there are 2 choices for that spot, and similarly two for the next spot and the next and the last. So there are 2^4 =16 combinations of 1 and 4 if we make 4 digit numbers. (this uses the multiplication rule)

To help a little more to see it, look at just the two digit number, It should have 2^2=4 choices by the logic above.

Here they are:

11,14,41,44 and that's it!.

See how we had two choices for each digit?

First answer by Mathdoc. Last edit by Mathdoc. Contributor trust: 424 [recommend contributor ]. Question popularity: 2 [recommend question].

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