Hi All,

We're told that the number of coronary-bypass operations performed in the United States increased from 13,000 to 191,000. We're asked for the approximate percent increase that this increase in the number of coronary-bypass operations represents. When a question asks about Percent Change, then the most direct way to get the correct answer is usually to just use the Percentage Change Formula (as some of the other explanations in this thread have done). There is another way to think about Percent Change though that can also get you the correct answer...

A 100% increase means that you added a positive number to itself. For example:
If you increase 13,000 to 26,000, then you have a 100% increase.
If you increase 13,000 to 39,000, then that would be a 200% increase.
If you increase 13,000 to 52,000, then that would be a 300% increase.
Etc.

Thus, if you can count up the approximate number of 13,000 'increases' that turn 13,000 into 191,000, then you'll have the approximate Percent Increase. Ultimately, this is just another way of using the concepts behind the Percent Change formula...

13 to......
26 to 39 to 52 to 65 to 78 to....
91 to 104 to 117 to 130 to 143 to....
156 to 169 to 182 to 195

That's approximately 14 increases, so approximately 1400%

Final Answer: D

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