GMAT Math : Arithmetic

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #51 : Understanding The Properties Of Integers

What is the greatest common factor of  and , where  is a postive integer?

Possible Answers:

Correct answer:

Explanation:

Firstly, we should start by noticing that  and  are co-prime, which means that they only share 1 as a common factor. It is due to the fact that they are consecutive integers. Also we should notice that  will never include  since it is the product from all integers from 1 to , therefore,  is not a factor of  

Example Question #221 : Arithmetic

What is the greatest common factor of  and ?

Possible Answers:

Correct answer:

Explanation:

To find the greatest common factor of two numbers, we must first write their respective prime factorization, in other words, we must write these numbers as a product of prime numbers. This can be done by firstly dividing a given number by 2, then 3, and all the way up to higher prime numbers. 

 and 

Then we simply have to multiply all the common factors, with their lowest power:

The common factors here are only 5's, and the lowest power of 5 in both numbers is . Therefore, the greatest common factor is .

Example Question #57 : Understanding The Properties Of Integers

What is the greatest common factor of  and ?

Possible Answers:

Correct answer:

Explanation:

We start by writing the prime factorization of these two numbers:  and 

Note that to find the prime factorization there is not much to do other than just starting with the smallest prime numbers and the GMAT requires to know the prime numbers under 100.

The common factors are only 2's, and we apply to this common factor of the lowest power, which is 1. Therefore, the final answer is .

Example Question #58 : Understanding The Properties Of Integers

What is the greatest common factor of  and ?

Possible Answers:

Correct answer:

Explanation:

We start by writing the prime factorization of these two numbers: 

 and .

By taking the common factors and raising them to the lowest power, we get  or , which is the final answer.

Example Question #1771 : Problem Solving Questions

What is the least common multiple of  and ?

Possible Answers:

Correct answer:

Explanation:

For the least common multiple, we also need to write out the prime factorization of these numbers, as follows: 

 and .

Then, we multiply all the factors raised to their highest powers.

Here we have: , which is equal to .

Example Question #222 : Arithmetic

What is the least common multiple of  and ?

Possible Answers:

Correct answer:

Explanation:

We begin by writing the prime factorization of 78 and 36. 

 and .

The rule to find the least common multiple is to multiply all factors raised to their highest power.

Here we have:  or .

Example Question #222 : Arithmetic

What is the least common multiple of  and ?

Possible Answers:

Correct answer:

Explanation:

Let's start by writing the prime factorization of these two numbers: 

 and .

Then we just have to multiply each factor raised to its highet power for common factors, as follows:

 or .

Example Question #1773 : Problem Solving Questions

You know that  and that the greatest common divisor of  and  is . What is the least common multiple of  and

Possible Answers:

Correct answer:

Explanation:

For any positive integer  and ,  being their least common multiple and  being their greatest common factor, then .

Therefore,

  or .

Example Question #61 : Understanding The Properties Of Integers

 and the greatest common divisor of  and  is , what is the least common multiple of  and ?

Possible Answers:

Correct answer:

Explanation:

We can use the property that for  and , whose greatest common factor is  and whose least common multiple is , then .

Therefore,

  or .

Example Question #225 : Arithmetic

 , and the least common multiple of  and  is , what is their greatest common factor?

Possible Answers:

Correct answer:

Explanation:

Using the property

  then, .

Notice that the GCD or greatest common divisor is the same thing as the GCF, or greatest common factor.

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