Thread: Easy thing about divisors

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

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

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

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.

Thanks in advance.

Greetings

EB

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.

Thanks in advance.

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

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

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.

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