Problem Solving

Hi All,

We're told that during a recent storm, 9 neighborhoods experienced power failures of durations 34, 29, 27, 46, 18, 25, 12, 35, and 16 minutes, respectively. We're asked for the MEDIAN duration, in minutes, of these power failures. The word "median" is a statistical term that means "middle number"; to properly define the MEDIAN of a group of numbers, we have to put the numbers in order from least to greatest and then find the one in the exact 'middle' of the list.

With this question, we have a minor 'shortcut': we know that there are 9 numbers, so if we list the 5 LOWEST numbers, then we know that the fifth number in that group will be the median of the 9 numbers. To start, we can see that each number is two digits. Notice that three of the numbers begin with a '1': 12, 16 and 18 - so we know that those are the lowest 3 numbers. Next, let's look for the numbers that begin with a '2': 25, 27 and 29. The lowest two numbers of that threesome are 25 and 27 - thus, the five lowest numbers are 12, 16, 18, 25 and 27... so 27 must be the median (and we don't actually have to list out the remaining numbers).

Final Answer: C

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

BTGmoderatorDC wrote:During a recent storm, 9 neighborhoods experienced power failures of durations 34, 29, 27, 46, 18, 25, 12, 35, and 16 minutes, respectively. For these 9 neighborhoods, what was the median duration, in minutes, of the power failures?

A. 34

B. 29

C. 27

D. 25

E. 18

Ordering from least to greatest, we have:

12, 16, 18, 25, 27, 29, 34, 35, 46

The median is the middle value. We can use the formula (n + 1)/2 to determine which data value is the median, and we obtain (9 + 1)/2 = 10/2 = 5. This means that the 5th data value is the median. Thus, the median is 27.

Answer: C