Carcass wrote:
Which of the following has as many positive factors as 300 have?
A) 200
B) 400
C) 500
D) 600
E) 700
---------ASIDE---------------------------------
If N = (p^a)(q^b)(r^c)..., where p, q, r,...(etc.) are prime numbers, then the total number of positive divisors of N is equal to (a+1)(b+1)(c+1)...Example: 14000 = (2^
4)(5^
3)(7^
1)
So, the number of positive divisors of 14000 = (
4+1)(
3+1)(
1+1) = (5)(4)(2) = 40
---------NOW ONTO THE QUESTION--------------------------
300 = (2^
2)(3^
1)(5^
2)
So, the number of positive divisors of 300 = (
2+1)(
1+1)(
2+1) = (3)(2)(3) = 18
Now check the answer choices....
NOTE: this is one of those questions that require us to check/test each answer choice. In these situations,
always check the answer choices from E to A, because the correct answer is typically closer to the bottom than to the top.
E) 700700 = (2^
2)(5^
2)(7^
1)
So, the number of positive divisors of 700 = (
2+1)(
2+1)(
1+1) = (3)(3)(2) = 18
We have a MATCH!!
Answer: E