Is n(n+1)(n+2) divisible by 24?

Question

(1) n is even
(2) (n+1) is divisible by 3 but not by 6

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Harley1980 · Accepted Answer

We know that  24=2^3*3 
So we should check if  n(n+1)(n+2)  contains  2^3  and  3

(we should keep in mind that when  n  or  n+1  or  n+2  equal to  0 , then product of all this numbers will be equal to  0  and divisible by  24 )

1) if  n  is even than  n+2  contain at least  2^2  and as  n  is even and not zero than  n+1  will be contain  3 . So  n(n+1)(n+2)  will be always divisible on  24 
Sufficient

2) from this statement we can infer that  (n+1)  is odd and contain  3  and that  n  is even and  n * (n+2)  contains at least  2^3 . So  n(n+1)(n+2)  will be always divisible on  24 
Sufficient

Answer is D

PrepTap · Answer

When n is even n(n+1)(n+2) is always divisible by 8 and 3. Hence it will be divisible by 8*3 = 24 For the explanation look at: solving-complex-problems-using-number-line-197045.html#p1521230 Statement 1: n is even Sufficient Statement 2: n+1 is divisible by 3 but not by 6 -> n+1 is odd -> n is even Sufficient Answer: Option (D)

thangvietnam · Answer

if n is even 
n=2k
n(n+2)= 2k(2k+2)=4.k.(k+1)
k(K+1) must be even because 2 consecutive number
so, n(n+2) is divisible by 8
n+1 is divisible by 3
so, the first condition is divisible by 24

thangvietnam · Answer

be careful

n(n+1)(n+2)
is 3 consecutive numbers, one of them must be divided by 3.
n is even , then n=2k, n+2=2(K+1)
n(n+2)=2k*2(k+1)=4k(k+1), 
k and k+1 is 2 consecutive interger, one of them must be divided by 2
so 4k(k+1) must be divided by 8
so, the total expresstion is divided by 24

we can pick specific numbers and find the answer,

condition 2
n+1 is divided by 3 but not 6. this mean n+1 is odd . this mean n and n+2 is two consecutive even number, product of which are multiple of 8 as I prove above.
sufficient.

the takeaway is that
the product of 2 consecutive even numbers is divided by 8. remember how to prove this
if there are 3 consecutive numbers, one of them must be divided by 3

those concept is tested many times on gmat because it is basic

ksrutisagar · Answer

St 1 : n is even

Minimum value of n = 2

(n) (n+1) (n+2) in this case = 2 * 3 * 4 = 24 Yes

For higher even values of n, (n) (n+1) (n+2) is a higher multiple of 24

Definite Yes

Sufficient

St 2 : (n + 1) is a divisible by 3 but not by 6

Which means (n+1) is a odd multiple of 3

So (n + 1) is odd as 3 is odd

This implies n is even

Definite yes as seen from St 1

Sufficient

Choice D

sayan640 · Answer

Minimum value of n can be zero also. 
 If n = zero , the entire numerator will be zero and be divisible by 24. 
The answer will be YES in that case.

Bunuel   VeritasKarishma

Bunuel · Answer

Well, n is even means that n is ..., -6, -4, -2, 0, 2, 4, 6, 8, .... So, n can be a negative even number too, not only 0 or positive even number. That changes nothing though, (1) is still sufficient.

aadrikacharya · Answer

why are taking the minimum value of n = 2 , and not 4, 6, 8 for that matter (it has not been mentioned anywhere to take the minimum <even> value of n) ?

Bunuel · Answer

If you check  this post  you'll see that n can be ANY even number: ..., -6, -4, -2, 0, 2, 4, 6, 8, .... So, there is no minimum value of n there.

P.S. Even though this does not change the answer but proper GMAT question would mention in the stem that n is a positive integer.

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Is n(n+1)(n+2) divisible by 24?

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Is n(n+1)(n+2) divisible by 24?

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