Hi swerve,

We're told that Pat took "N" whole days to complete the project and that one of the answers represents the value of N (with the dash representing a digit which has been omitted from the 4-digit value of N). We're asked which of the following COULD be the value of N. While this question might look a bit weird, it's built on a specific 'rule of division' that you can use to quickly answer the question.

To start, since we're dealing with WHOLE days, the total number of hours MUST be a multiple of 24. By extension, any number that is a multiple of 24 is ALSO a multiple of 4, so we can use the 'rule of 4' to determine which answers are multiples of 4 and which are not.

For a number to be divisible by 4, the last 2 digits of the number must for a number that is divisible by 4. For example:

112 IS divisible by 4 because '12' is divisible by 4.
115 is NOT divisible by 4 because '15' is not divisible by 4.

Of the 5 answers, only one of them has a 'last 2 digits' that is divisible by 4: "6_36" (since 36 is divisible by 4). Since this is the only answer that fits that pattern, it must be the answer.

Final Answer: B

GMAT assassins aren't born, they're made,
Rich

swerve wrote:Pat took "N" whole days to complete the project. If the dash represents the digit which has been omitted, then which of the following could be the number of hours that he took to complete the project?

A. 6_98
B. 6_36
C. 6_50
D. 6_90
E. 8_62

Since there are 24 hours in a day, the number needs to be divisible by 24. Any number divisible by 24 must also be divisible by 4. A number is divisible by 4 when the last two digits of that number are divisible by 4. Since 36/4 = integer, 6_36 is the correct answer.

Answer: B