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by sud21 » Sun Jan 15, 2012 2:26 am
A list of consecutive natural numbers contains 9 and 15. Does the list contain number which can be divisible by 8?
1). The list has 10 numbers.
2). 18 is in the list.
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Source: — Data Sufficiency |
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by rijul007 » Sun Jan 15, 2012 5:04 am
sud21 wrote:A list of consecutive natural numbers contains 9 and 15. Does the list contain number which can be divisible by 8?
1). The list has 10 numbers.
2). 18 is in the list.

1). The list has 10 numbers.
The list can be:
consecutive integers 9-18, 8-17, 7-16 or 6-15
Each of them contains number divisible by 8
Suff


2). 18 is in the list.
The list consists of consecutive natural numbers.
9, 15 and 18 are one of the numbers
16 must be in the list
Suff

Option D
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by Brent@GMATPrepNow » Sun Jan 15, 2012 3:11 pm
sud21 wrote:A list of consecutive natural numbers contains 9 and 15. Does the list contain number which can be divisible by 8?
1). The list has 10 numbers.
2). 18 is in the list.
Statement 1:
There's a useful rule that says, "If there are n consecutive integers in a set, then 1 of those numbers must be divisible by n."

Since statement 1 tells us that the list contains 10 consecutive integers, we know that it must also contain 8 consecutive integers, which means we are guaranteed to have a number that is divisible by 8.
So, statement 1 is SUFFICIENT

Statement 2:
If the list contains consecutive integers, and if the list contains 15 and 18, then the list must also contain 16 and 17.
Since 16 is in the list, we are guaranteed to have a number that is divisible by 8.
So, statement 2 is SUFFICIENT

The answer is D

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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