Need help with uh...math problem...

[Mark]

I need with with reducing big fractions. The small ones are easy but it's the big ones that confuse me. For example:

6489/7931




I read the instructions on this page but I don't understand how they used the numbers 2, 2, 3, 5, and 7 when they were dividing. For example, when they did the problem 3150/2 and got 1575 as the answer, why did they divide by 3 now instead of the 2? Then a few steps later, they divide by 5 and not 3 anymore...




If someone can help me clearly understand this, id greatly appreciate it...

 

[notfred]

9/11

 

[Mark]

I know that's the answer but I need to know how to do it by hand since my teacher doesn't allow calculators...

 

[eLiu]

just divide by #s...if you cant see the "bigger" relationships, then divide by small primes...start with say 2...if it doesnt divide, try 3, 5, 7, etc etc

that method is kinda slow...but until you can see the relationships, it's the only way.

-eric

 

[notfred]

<< I know that's the answer but I need to know how to do it by hand since my teacher doesn't allow calculators... >>



no offense, but are you in like 8th grade?

 

[Mark]

No, but he's a moron who can't teach.

 

[isasir]

As eLiu mentioned, you just need to divide by numbers like 2,3,5,7,11 (prime numbers) til you can't evenly divide anymore. I guess a couple of "tricks" would be to know that if a number is even, then you'd want to divide by 2. If a number ends in a 5, then divide by 5. Uh, if the numbers added together continously til you get a single digit add up to 9 (ie: 18027 = 1+8+0+2+7=18; 1+8=9), then you can divide by 9. otherwise, just divide by 3. keep working your way up if none of these numbers divide evenly.