This question has a great "pattern-matching" shortcut built into it, but you'll have to pay attention to the answer choices to see it.
We're told that a store owner raises the price of an item by 10%. We're asked which of the 5 answers could NOT possibly be the new price.
In this scenario, it's real easy to come up with a simple example of what the store owner did.
price = $1, then new price = $1.10
You'll notice that answer is Answer A.
Answer B is just 8 times $1.10, which makes sense because 10% of 8 is 0.80...
price = $8, then new price = $8.80
So the shortcut is just to find the answers that are multiples of $1.10
Answer C is another quick "find" - it's 10 times $1.10
Between D and E, you have to do a little work, but if you "break down" E, you get....
78.10 = 77.00 + 1.10
77.00 = 70 + 7 (which is 10% of 70)
1.10 = 1 + 0.1 (which is 10% of 1)
So E is another multiple of $1.10
That leaves just one answer....
GMAT assassins aren't born, they're made,
Official Guide 2016 Question Breakdown:
GMAT Club Verified Reviews for EMPOWERgmat & Special Discount
EMPOWERgmat Podcast - A Wild Secret About The GMAT Algorithm