Solution to Problem 7

Solution by Mike ArsenaultThe answer to problem 7 is that 1/3 can be written as:

0.2 in base 6
0.22222..... in base 7
0.252525.... in base 8

Here is the demonstration of how I arrived at both the base 6 and base 7 answers; base 8 was done the same way - I'm just too lazy to type it in as well :-).

The way that you can determine 1/3 = 0.33333.... in base 10 is to perform the long division:

          0.33333.....        ---------        3 | 1.00000            9          ----            10             9            ---             10

.... and so on

So if we were to perform the same operation in base 6, knowing that the 3 times table (in base 6) is as follows

3 x 0 = 03 x 1 = 33 x 2 = 103 x 3 = 133 x 4 = 203 x 5 = 23the division would look like:          0.2        ------        3 | 1.0          1 0          ----            0

so therefore 1/3 in base 6 is 0.2.

This can be confirmed by doing the multiplication:

        3 x 0.2 in base 6 (ensuring that the result is 1)is the same as        (3 x 6^0) x (2 x 6^(-1)) converted to base 10        (3 x 1) x (2 x 1/6)         3    x    1/3         1The multiplication confirmed the division.....----------------------------------------In base 7, the 3 times table is:3 x 0 = 03 x 1 = 33 x 2 = 63 x 3 = 123 x 4 = 153 x 5 = 213 x 6 = 24The long division is .....          0.222.....        -------        3 | 1.000            6          ----            10             6            ---             10To confirm this with multiplication       3 x 0.22222..... in base 7can be written as (in base 10)        (3 x 7^0) x (2x7^(-1) + 2x7^(-2) + 2x7^(-3) + .... )            3     x (2/7 + 2/49 + 2/343 + 2/2401 + .....)          3     x (0.3331945 + .....)which is equal to 1.
[Editorial note: The sum in the last calculation is a geometric series, equal to (2/7)/(1-(1/7)) = 1/3.]
Also solved by Brian Gregory and Christophe Mentz. Brian asks the related question, "What does 0.33333... correspond to in the various bases?"
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