Carcass wrote:
The price of a car was m dollars. It then depreciated by x%. Later, it appreciated by y% to n dollars. If there are no other changes in the price and if y = \(\frac{x}{1-\frac{x}{100}}\) , then which one of the following must n equal?
(A) \(\frac{3m}{4}\)
(B) \(m\)
(C) \(\frac{4m}{3}\)
(D) \(\frac{3m}{2}\)
(E) \(2m\)
Choose \(m = 100\), \(x = 25\)
\(y =\) \(\frac{25}{(1-25/100)}\)
\(y =\) \(\frac{25}{(3/4)}\)
\(y = 25 * \frac{4}{3}\)
\(y = \frac{100}{3}\)
\(y = 33.3\)
\(y = \frac{1}{3}\)
So \(m\) depreciates by 25%. That means:
\(100(1-\frac{1}{4})\)
\(100(\frac{3}{4})\)
\(100(\frac{3}{4})\) is the price after the depreciation. We're keeping this the way it is, and you'll see why next.
After the depreciation, the new price appreciated by y%. This means that:
\(100(\frac{3}{4})(\frac{4}{3})\) =
\(100\).
So in the end, the price never changed.
The answer is B