
Kevin S. answered 03/07/13
Look for a common factor. Since both numbers are even, 2 is a common factor:
7272/10000 = (2)(3636)/(2)(5000) = 3636/5000
These are still even, so we can try 2 again... BUT... we could be awhile...
Let's look at the divisibility rules:
A number is divisible by:
- 2 if the number is even
- 3 if the sum of the digits of the number is divisible by 3
- 4 if the last two digits of the number is divisible by 4
- 5 if the number ends in 5 or 0
- 6 if the number is even AND divisible by 3
- 8 if the last three digits of the number is divisible by 8
- 9 if the sum of the digits of the number is divisible by 9
(what about 7? There is a rule, but it's so obscure that it's just as easy to test it via division)
So...
272 is divisible by 8 (8 * 34 = 272), so 7272 is divisible by 8. 1000 is divisible by 8, s0 10000 is divisible by 8 as well.
7272/10000 = 909/1250.
Now, let's reexamine the divisibility rules for both top and bottom:
909 - odd, divisible by 3 and 9, but not by 2, 4, 5, 6, or 8
1250 - even, divisible by 2, 5, but not by 3, 4, 6, 7, 8, or 9
Since we have no other common factors, our answer is 909/1250