• Sep 30th 2006, 06:38 AM
Rocher
I forgot it over the summer lol. I need help finding the GCF of 51,68, 86. Thx lol!!
• Sep 30th 2006, 06:58 AM
earboth
Quote:

Originally Posted by Rocher
I forgot it over the summer lol. I need help finding the GCF of 51,68, 86. Thx lol!!

Hello,

use prime factors:
51 = 3 * 17
68 = 4 * 13
86 = 2 * 43

Each product must be in the GCF. So the GCF = 3 * 4 * 13 * 17 * 43.

That's a pretty big number!.

Greetings

EB
• Sep 30th 2006, 08:03 AM
CaptainBlack
Quote:

Originally Posted by Rocher
I forgot it over the summer lol. I need help finding the GCF of 51,68, 86. Thx lol!!

First factorise 51 = 3x3x7
then 68 = 2x2x17
finally 86=2x43.

Since these do not have a common prime factor the greatest common factor
of 51, 68, 86 is 1.

RonL
• Sep 30th 2006, 11:20 AM
earboth
Quote:

Originally Posted by CaptainBlack
First factorise 51 = 3x3x7
then 68 = 2x2x17
finally 86=2x43.

Since these do not have a common prime factor the greatest common factor
of 51, 68, 86 is 1.

RonL

Hello,

I obviously made a big mistake. I'm sorry.
But could you please explain the difference between GCF and GCD. Otherwise I'm going to mess it again.

Greetings

EB
• Sep 30th 2006, 11:48 AM
Quick
Quote:

Originally Posted by earboth
GreetingsHello,

I obviously made a big mistake. I'm sorry.
But could you please explain the difference between GCF and GCD. Otherwise I'm going to mess it again.

Greetings

EB

GCF stands for "Greatest Common Factor" which is the largest number that goes into the chosen numbers. Such as the greatest common factor for 10 and 15 is 5.

What you probly meant was the Lowest Common Multiple, which is the smallest number that two different numbers go into.

Such as the LCM for 10 and 15 is 30
• Sep 30th 2006, 11:57 AM
CaptainBlack
Quote:

Originally Posted by earboth
Hello,

I obviously made a big mistake. I'm sorry.
But could you please explain the difference between GCF and GCD. Otherwise I'm going to mess it again.

They are the same thing, what I think you were computing was the least
common multiple. (LCM)

RonL
• Sep 30th 2006, 03:36 PM
ThePerfectHacker
Quote:

Originally Posted by Rocher
I forgot it over the summer lol. I need help finding the GCF of 51,68, 86. Thx lol!!

There is an easier way to do it.

It can be shown that, (for positive numbers)
gcd(a,b,c)=gcd(gcd(a,b),c)
Now, instead doing all three first find,
gcd(51,68)

And using that result find the gcd with 86.
• Sep 30th 2006, 04:10 PM
CaptainBlack
Quote:

Originally Posted by ThePerfectHacker
There is an easier way to do it.

It can be shown that, (for positive numbers)
gcd(a,b,c)=gcd(gcd(a,b),c)
Now, instead doing all three first find,
gcd(51,68)

And using that result find the gcd with 86.

In fact since gcd(51,68)=1 you don't have to check 86, as we know
that the result will be 1.

RonL