Bunuel wrote:
A candy bar originally costs x cents per y ounces. If the size of the candy bar is reduced by 1 ounce and the price is increased by 10%, what is the new cost of the candy bar, expressed in cents per ounce?
A. (x - y)/10
B. 11(x - y)/10
C. 11x/(11y)
D. 11x/(10(y - 1))
E. 11x/(1 - y)
In addition to the Alternative approaches (using numbers) shown above, we'll also show a Logical approach based on the properties of percents.
The original price was x/y cents per ounce. Increasing this by 10% gives 1.1x/y = 11x/10y cents per ounce.
Our answer must be a little bit larger than this because we're charging the money for less ounces of chocolate.
(A),(B) don't make any sense because they don't give a ratio between x and y.
(C) is the original price and doesn't show an increase.
(E) looks a bit odd because it doesn't show something close to an 11/10 ratio (also, it is negative: y > 1 because otherwise we couldn't reduce the chocolate by 1 ounce).
(D) must be our answer.
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