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HAMAYUN · Dec 9, 2009, 03:55 PM

15w+21

tickle · Dec 9, 2009, 04:15 PM

What is 'fign gcf', hamayun??

HAMAYUN · Dec 9, 2009, 04:18 PM

Originally Posted by tickle

what is 'fign gcf', hamayun ?????

Greatest common factor

Perito · Dec 9, 2009, 05:24 PM

Originally Posted by HAMAYUN

15w+21

15 = 3 x 5
21 = 3 x 7

3 is the common factor -- and, for that matter, it is the greatest common factor. It is also a common factor of 15w.

HAMAYUN · Dec 9, 2009, 05:26 PM

Originally Posted by Perito

15 = 3 x 5
21 = 3 x 7

3 is the common factor -- and, for that matter, it is the greatest common factor. It is also a common factor of 15w.

I have to multiply and what is the biggest number that has the number I'm looking for

Perito · Dec 9, 2009, 08:46 PM

You examine the prime factors. Select the factors that are the same in both cases. If a factor occurs twice or more times, then select the number of factors that occur the same number of times for both values. Then, multiply the common factors together.

For example, pick two numbers: 840 and 1260

840 = 2 x 2 x 2 x 3 x 5 x 7
1260 = 2 x 2 x 3 x 3 x 5 x 7

"2" appears as a factor three times in the first group and twice in the second. Thus, there are TWO 2's in common.

"3" appears once in common

"5" and "7" appear once in common

Thus, the common factor is 2 x 2 x 3 x 5 x 7 = 420.

420 is a factor of both 1260 and 840, and because of the way we determined it, we can be assured that there is no larger common factor. Therefore, it is the greatest common factor. QED