If n=2^4*3*5, how many factors of n are greater than or equal to 8 and less than equal to 30?
(A) 8
(B) 9
(C) 10
(D) 12
(E) 15
The OA is A.
Please, can any expert explain this PS question for me? I have many difficulties to understand why that is the correct answer. Thanks.
If n=2^4*3*5, how many factors of n are...
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- ceilidh.erickson
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There may be more formulaic strategies that you could use, but in this case (since it's a small-ish range), I'd just list out all the factors, then count:
n=2^4*3*5
Factors:
1
2
3
4
5
6
8
10
12
15
16
20
24
30
There are 8 distinct factors in this range. The answer is A.
Please list the source of your question!
n=2^4*3*5
Factors:
1
2
3
4
5
6
8
10
12
15
16
20
24
30
There are 8 distinct factors in this range. The answer is A.
Please list the source of your question!
Ceilidh Erickson
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
EdM in Mind, Brain, and Education
Harvard Graduate School of Education
GMAT/MBA Expert
- Scott@TargetTestPrep
- GMAT Instructor
- Posts: 7264
- Joined: Sat Apr 25, 2015 10:56 am
- Location: Los Angeles, CA
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The factors of n that are greater than or equal to 8 and less than or equal to 30 are:swerve wrote:If n=2^4*3*5, how many factors of n are greater than or equal to 8 and less than equal to 30?
(A) 8
(B) 9
(C) 10
(D) 12
(E) 15
The OA is A.
Please, can any expert explain this PS question for me? I have many difficulties to understand why that is the correct answer. Thanks.
3 x 5 = 15
2 x 5 = 10
2 x 3 x 5 = 30
2^2 x 3 = 12
2^2 x 5 = 20
2^3 = 8
2^3 x 3 = 24
and
2^4 = 16
So there are 8 such factors.
Answer: A
Scott Woodbury-Stewart
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