Pluggin in answers vs number properties

Hi JJMforthegold,

TESTing THE ANSWERS is a perfect approach for this type of question - simply plug in the options until you find the one that 'fits' what the prompt describes. There are some Number Properties involved in this question that might help you on other prompts though, so I'll review them here:

101/1 = 101 Dividing an integer by 1 will always lead to the same integer (you probably knew this one already)

102/2 = 51 Dividing any even integer by 2 will always lead to an integer

103/3 = 34 1/3 To determine whether an integer is evenly divisible by 3 or not, you can use the 'rule of 3' (if the DIGITS of the number sum to a total that is divisible by 3, then the number is divisible by 3). For example:
27 IS divisible by 3 because 2+7 = 9. Since 9 is divisible by 3, 27 is divisible by 3.
26 is NOT divisible by 3 because 2+6 = 8. Since 8 is not divisible by 3, 26 is not divisible by 3.

Here, we're dealing with 103. 1+0+3 = 4. Since 4 is not divisible by 3, 103 is not divisible by 3.

104/4 = 26 If the last 2 digits of a number for a 2-digit number that is divisible by 4, then the larger number is divisible by 4.
For example:
104 is divisible by 4 because 04 is divisible by 4.
126 is NOT divisible by 4 because 26 is not divisible by 4.

105/5 = 21 If an integer ends in 5 (or 0), then dividing that integer by 5 will always lead to an integer.

Final Answer: C

GMAT assassins aren't born, they're made,
Rich

JJMforthegold wrote:For which of the following values of n is (100+n)/n NOT an integer?

a) 1
b) 2
c) 3
d) 4
e) 5
c

The GMAT loves to test the following rule:
(a + b)/c = a/c + b/c

Applying this rule, we get: (100+n)/n = 100/n + n/n = 100/n + 1
In order for 100/n + 1 to be an integer, it must be the case that 100/n is an integer.
In order for 100/n to be an integer, n must be a factor of 100
So, we can eliminate all answer choices that are factors of 100
So, ELIMINATE A, B, D and E

Answer: C

Cheers,
Brent