If n is a positive integer and 10^n is a factor of m, what is the value of n?
(1) m is the product of the first positive 40 integer numbers.
(2) n > 8*m/40!
The OA is the option C.
Why is C the correct option? Is not sufficient just with the statement (1)? Can you help me here? Please.<i class="em em-anguished"></i>
If n is a positive integer and 10^n is a factor of m
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Since the statements refer to 40!, determine options for n if 10^n is a factor of 40!.M7MBA wrote:If n is a positive integer and 10^n is a factor of m, what is the value of n?
(1) m is the product of the first positive 40 integer numbers.
(2) n > 8*m/40!
Since 10=2*5, EVERY COMBINATION OF 2*5 contained within the prime-factorization of 40! will enable 10^n to divide into 40!.
The prime-factorization of 40! includes FAR MORE 2'S than 5's.
Thus, the number of 10's that can divide into 40! depends on the NUMBER OF 5's contained within 40!.
To count the number of 5's, simply divide increasing POWERS OF 5 into 40.
Every multiple of 5 within 40! provides at least one 5:
40/5 = 8 --> eight 5's.
Every multiple of 5² within 40! provides a SECOND 5:
40/5² = 1 --> one more 5.
Thus, the total number of 5's contained within 40! = 8+1 = 9.
Since 40! contains nine 5's,10^n will divide into 40! if n≤9.
Statement 1: m = 40!
Since 10^n is a factor of 40!, n can be any positive integer less than or equal to 9.
Thus, the value of n cannot be determined.
INSUFFICIENT.
Statement 2: n > 8(m/40!)
Here, n can be any positive integer such that n > 8(m/40!).
Thus, the value of n cannot be determined.
INSUFFICIENT.
Statements combined:
Statement 1: n≤9.
Statement 2:
Substituting m=40! into n > 8(m/40!), we get:
n > 8(40!/40!)
n > 8.
Since n≤9 and n>8, only option is possible:
n=9.
SUFFICIENT.
The correct answer is C.
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I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
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