GMAT Math : Arithmetic
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Example Questions
Example Question #23 : Properties Of Integers
Add the squares of the prime numbers between 50 and 60.
There are two primes between 50 and 60 - 53 and 59. The sum of their squares is:
Example Question #1744 : Problem Solving Questions
What are the last two digits, in order, of 
Inspect the first few powers of 15; a pattern emerges.
After the first power, any odd power of 15 ends in the digits 75. Since 1,515 is odd, this is the correct choice.
Example Question #1741 : Gmat Quantitative Reasoning
Each box in this five-digit number is to be replaced by a digit to form a number divisible by 3:
How many ways can this be done using the same digit in each box?
A number that is divisible by 3 has digit sum that is divisible by 3. Let 
Substitute each of the integers from 0 to 9 for 
Therefore, there are three ways to fill the box in with the same digit to make the number a divisible by 3.
Example Question #24 : Properties Of Integers
What is the sum of the composite numbers between 1 and 100 inclusive that have 7 as their last digit?
The composite numbers in the 1-100 range that end in 7 are 27, 57, 77, and 87.
Add:
Example Question #25 : Properties Of Integers
Each box in this five-digit number is to be replaced by a digit to form a number divisible by 4:
How many ways can this be done using the same digit in each box?
Whether the integer is divisible by 4 is determined by the last two digits - the number is divisible by 4 if and only if the last two digits form a number itself divisible by 4. There are five digts that you can put in the box to achieve this - 1, 3, 5, 7, 9 (16, 36, 56, 76, and 96 all are evenly divisible by 4).
Example Question #26 : Properties Of Integers
Multiply all of the composite integers between 1 and 100 that have 3 as their last digit. What is the product?
The composite numbers in the 1-100 range that end in 3 are 33, 63, and 93. Multiply:
Example Question #31 : Understanding The Properties Of Integers
Add the composite numbers between 81 and 90 inclusive.
The only prime numbers from 81 to 90 are 83 and 89, so we add:
Example Question #32 : Understanding The Properties Of Integers
Add the prime numbers between 60 and 90.
The prime numbers between 60 and 90 are:
Add them:
Example Question #33 : Understanding The Properties Of Integers
Add the factors of 29.
29 is a prime number and therefore has two factors, 1 and itself. The sum of the two is 30.
Example Question #1751 : Gmat Quantitative Reasoning
How many integers from 71 to 100 inclusive do not have 2, 3, or 5 as a factor?
The factors of 2 are exactly the integers that end in 2, 4, 6, 8, or 0, and the factors of 5 are exactly the integers that end in 5 or 0. Therefore, we will start with the integers that end in 1, 3, 7, and 9, and eliminate the multiples of 3:
Of these, 81, 87, 93, and 99 are the only multiples of 3. Remove them and we have the set
a set of eight elements.
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