Identify which repeat and which terminate by not calculating. How do you know?
1. 1/40
2. 1/24
3. 2/125
4. 2/99
5. 7/300
6. 7/200
In a reduced form.....If we can express the denominator solely as a power of 2 or a power of 5 - or both - the fraction will terminate....else..it repeats.....
1/ 40 terminates = 1 / [ 2^3 * 5]
1/ 24 does not = 1 / [ 2^3 * 3 ]
2/125 terminates = 2 / 5^3
2/ 99 does not = 2 / [ 3^2 * 11]
7/ 300 does not = 7 / [ 2^2 * 5^2 * 3 ]
7 / 200 terminates = 7 / [ 2^3 * 5^2]
Here's the provision for the reduced form
3 / 300 appears to not terminate....however
3 / 300 = 1 / 100 = 1 / [ 2^2 * 5^2 ] so this actually does terminate !!!
And that's all there is to it !!!!
Thanks Chris,
I had not thought about that before.
To put it another way..
If the decimal is to terminate then
The prime factors of the denominator must ONLY be the prime factors of 10
(which are 2 and 5 )
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I assume this can be extended to other bases.
So
1/5 base 8 is a recurring decimal because the prime factors of 5 are not the prime factors 8
That works.
I just did the division
and got
\(\frac{1}{5_8}=0.14\bar6\bar3\) (base8)
How about that!
Thanks Chris