All SAT Math Resources
Example Questions
Example Question #81 : Integers
What's the greatest common factor of 81 and 27?
Let's do some divisibility rules. For , the sum of the digits must be divisible by .
We have:
They are both good so when we divide both numbers by , we get . Lastly they are both divisible by . So we multiply both factors to get an answer of .
Example Question #11 : Greatest Common Factor
What's the greatest common factor of 2, 6, 9, and 10?
Greatest common factor involves all the numbers in the set. Even though three of the numbers are divisble by , isn't. The only factor that satisfies all the numbers is .
Example Question #83 : Integers
What's the greatest common factor of 4, 8, 16, and 26?
Although the first three numbers are divisible by , doesn't divide evenly into . The next best factor is . The remainder will be . This won't go any further as most of the numbers are even except . Our final answer is just .
Example Question #22 : Factors / Multiples
What's the greatest common factor of 15, 90, 105, and 225?
We know all of the numbers are divisible by so when we divide all the numbers by , we have . Next, we can divide al of them by , because the sum of the digits of all numbers are divisible by . So we get . This is as best as we can go so now we multiply the factors to get as an answer.
Example Question #12 : Greatest Common Factor
What's the greatest common factor of 36, 84, 96, 120, and 264?
Because they are all even and divisible by , we can divide each number to get . Next, let's divide by to get . We are finished as we have a mixture of prime and composite numbers. We multiply the factors to get .
Example Question #731 : Arithmetic
Find the greatest common factor of and .
The key here is to find the prime factorizations of both numbers and multiplying the common prime factors together:
Both prime factorizations have in common, so is our answer.