SOLUTION: Please help. Thank you Choose the correct greatest common factor of 105 and 147 a) 21 b) 15 c) 63 d) 20

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: Please help. Thank you Choose the correct greatest common factor of 105 and 147 a) 21 b) 15 c) 63 d) 20      Log On


   



Question 117738: Please help. Thank you
Choose the correct greatest common factor of 105 and 147
a) 21 b) 15 c) 63 d) 20

Found 2 solutions by MathLover1, jim_thompson5910:
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!
The greatest+common+factor of two or more whole numbers is the largest+whole+number that divides+evenly into each of the numbers.

There are two ways to find the greatest common factor.

The first+method is to list all of the factors of each number, then list the common+factors and choose the largest+one.

the GCF of 105 and 147:
the factors of 105 are 1,+3, 5, 7, 15, 21,35 and 105
thefactors of 147 are 1,++3,+7,+21,+49 and 147
the common factors of 105 and 147 are 1, 3,+7,+21
Although the numbers in bold are all common factors of both 105 and 147, 21 is the greatest common factor.
The second+method for finding the greatest common factor is:
to list the+prime+factors, then multiply the common+prime+factors

The prime factorization of 105 and 147 is:
105+=3%2A5%2A7
147=3%2A7%2A7
Notice that the prime factorizations of 105 and 147 both have one+3 and one 7 in common.
So, we simply multiply these common prime factors to find the greatest common factor:
3+%2A7=+21

so, correct answer is: a) 21+

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
First, list the prime factorization of each number. If you need help with prime factorization, check out this solver.


105: 3*5*7


147: 3*7*7


Now highlight the factors that the two numbers share in common


105: 3*5*7


147: 3*7*7


Now pick one set of these highlighted numbers and multiply

3*7=21

So the GCF of 105 and 147 is 21


So the answer is A)