BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

factors

Expert replies
by niraj_a » Sun Dec 07, 2008 9:48 am
If 10^n is a factor of the product of the first 24 integers, what is the greatest possible value of n?

A) 7
B) 6
C) 5
D) 4
E) 3

OA D

i guesstimated 5 = n because 24*20*10*5*2 acount for 4 zeros anyway.
Join the discussion
Source: — Problem Solving |

Re: factors

by Stuart@KaplanGMAT » Sun Dec 07, 2008 9:59 am
niraj_a wrote:If 10^n is a factor of the product of the first 24 integers, what is the greatest possible value of n?

A) 7
B) 6
C) 5
D) 4
E) 3


i guesstimated 5 = n because 24*20*10*5*2 acount for 4 zeros anyway.
For every factor of 10, we need a 2 and a 5.

2 won't be the limiting factor (since every even number has at least 1 factor of 2), so let's focus on the 5s.

Looking at the relevant numbers in 24!:

5*10*15*20

means that we'll have 4 5s on our list. Therefore, the maximum number of 10s we can get is also going to be 4.
Image

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
Join the discussion