GRE Prep Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
If an integer n is chosen from the integers 1
[#permalink]
28 Nov 2019, 00:04
28 Nov 2019, 00:04
00:00
Question Stats:
44% (01:34) correct
56% (01:43) wrong based on 25 sessions
Hide Show timer Statistics
If an integer n is chosen from the integers 1 through 72,what is the probability that n*(n+1)*(n+2)will be divisible by 8
(a)1/4
(b)3/8
(c)1/2
(d)5/8
(e)3/4
(a)1/4
(b)3/8
(c)1/2
(d)5/8
(e)3/4
Re: If an integer n is chosen from the integers 1
[#permalink]
28 Nov 2019, 00:10
28 Nov 2019, 00:10
1
Expert Reply
1
Bookmarks
n is Even
Since n is divisible by 2 then either one of n or n+2 will be divisible by 4. Hence the product ?(?+1)(?+2)will be divisible by 8. Total choices 36.
n is Odd
Then n and n+2 will both be odd and the only way this expression is divisible by 8 is when n+1 is divisible by 8. There are 72/8 such choices : (7,15,23,..,71).
So, combining 1 and 2 we have 36 + 9 = 45 choices for n. Which results in a probability of 45/72=5/8
This is not a GRE. You are doing the wrong practice
Since n is divisible by 2 then either one of n or n+2 will be divisible by 4. Hence the product ?(?+1)(?+2)will be divisible by 8. Total choices 36.
n is Odd
Then n and n+2 will both be odd and the only way this expression is divisible by 8 is when n+1 is divisible by 8. There are 72/8 such choices : (7,15,23,..,71).
So, combining 1 and 2 we have 36 + 9 = 45 choices for n. Which results in a probability of 45/72=5/8
This is not a GRE. You are doing the wrong practice
Re: If an integer n is chosen from the integers 1
[#permalink]
06 Dec 2019, 03:38
06 Dec 2019, 03:38
Carcass wrote:
n is Even
Since n is divisible by 2 then either one of n or n+2 will be divisible by 4. Hence the product ?(?+1)(?+2)will be divisible by 8. Total choices 36.
n is Odd
Then n and n+2 will both be odd and the only way this expression is divisible by 8 is when n+1 is divisible by 8. There are 72/8 such choices : (7,15,23,..,71).
So, combining 1 and 2 we have 36 + 9 = 45 choices for n. Which results in a probability of 45/72=5/8
This is not a GRE. You are doing the wrong practice
Since n is divisible by 2 then either one of n or n+2 will be divisible by 4. Hence the product ?(?+1)(?+2)will be divisible by 8. Total choices 36.
n is Odd
Then n and n+2 will both be odd and the only way this expression is divisible by 8 is when n+1 is divisible by 8. There are 72/8 such choices : (7,15,23,..,71).
So, combining 1 and 2 we have 36 + 9 = 45 choices for n. Which results in a probability of 45/72=5/8
This is not a GRE. You are doing the wrong practice
(7,15,23,..,71) This case has already been counted as n being even(70). So the total cases are 44
It's a GRE question. I have the same username on GMAT club, so won't post a GMAT question here.
