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Source: — Data Sufficiency |
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by stop@800 » Fri Oct 03, 2008 1:11 am
lets say 5n/18 is 2

so n is 36/5
and

n/18 is 2/5 which is not an integer


Similarly for 3n/18


Now A+B
5n/18 is integer 1

3n/18 is an integer
6n/18 is also integer 2

subtract 1 from 2
so n/18 is integer
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Re: MGMAT

by 4meonly » Sun Oct 05, 2008 5:03 am
raju232007 wrote:Is n/18 an integer
1. 5n/18 is an integer
2.3n/18 is an integer
The ans is C....Kindly explain.

to make n/18 an integer n should have 2*3^2 as factors
So we must prove that n has these factors

(1)
5n/18 is an integer
If the result will be any multiply of 5, then n/18 will be an integer
but here it is not mentioned
INSUFF

(2)
3n/18 is an integer
n/6 is an integer
n can be 6, 12, 18 etc.
INSUFF

(1) and (2) tha same as stop@800
5n/18 is integer 1

3n/18 is an integer
6n/18 is also integer 2

subtract 1 from 2
so n/18 is integer

C
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by praneeth » Sun Nov 09, 2008 8:08 am
stop@800 wrote:lets say 5n/18 is 2

so n is 36/5
and

n/18 is 2/5 which is not an integer


Similarly for 3n/18


Now A+B
5n/18 is integer 1

3n/18 is an integer
6n/18 is also integer 2

subtract 1 from 2
so n/18 is integer
Would the answer to this question be different if we knew n was an integer to start with?

If n is an integer, then n/18 cannot have a 5 in the denominator, therefore the only way 5n/18 can be an integer is if n / 18 is an integer?
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by EricLien9122 » Sun Nov 09, 2008 10:18 am
You sure answer is C? I came up with A.

Q: n/18=int?

1. 5n/18=int. n has to be multiple of 18 in order to satisfy this statement.

Sufficient.

2. 3n/18=int, n actually is a multiple of 6 for the statement.

Insufficient.


Please correct me if I made a mistake.
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by stop@800 » Sun Nov 09, 2008 10:54 am
EricLien9122 wrote:You sure answer is C? I came up with A.

Q: n/18=int?

1. 5n/18=int. n has to be multiple of 18 in order to satisfy this statement.

Sufficient.

2. 3n/18=int, n actually is a multiple of 6 for the statement.

Insufficient.


Please correct me if I made a mistake.
You can not assume n to be an integer.
Its not given

Hope this helps
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by logitech » Sun Nov 09, 2008 11:39 am
stop@800 wrote:Now A+B
5n/18 is integer 1

3n/18 is an integer
6n/18 is also integer 2

subtract 1 from 2
so n/18 is integer
Smart!! :!:
LGTCH
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by somail » Mon Nov 10, 2008 9:27 am
Can someone please go into further detail as to why the answer is not A?

We are asked is n/18 and int ---> n/(3*3*2)

Given: 5n/18 is an int ---> 5n/(3*3*2)

in order for statement 1 to be true, n must contain 3*3*2. Thus making A sufficient.

Why is this wrong?


Thanks
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by EricLien9122 » Mon Nov 10, 2008 2:00 pm
somail:

N can equal to a fraction that can give an integer answer for statement 1.

if N=18/5

5*(18/5)/18=1, which satisfy the statement

plug is back to the question...

(18/5)/18= 1/5 answer would be no.

If N=18, then answer is yes.

Therefore statement 1 is not sufficient.


Please correct me if I made a mistake.
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Re: MGMAT

by yezz » Mon Nov 10, 2008 2:14 pm
Is n/18 an integer

1. 5n/18 is an integer

2.3n/18 is an integer

IS N = 18X

FROM 1

5N = 18B
N = 18/5 B IF B IS A MULTIPLE OF 5 THEN N IS INTIGER..WE DONT KNOW .......INSUFF

FROM2

3N/18 = C

N = 6C.......N IS INTIGER.......b
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