A certain novel is available in hardcover and paperback. If the store stocks a total of 100 copies of this book, how many are paperbacks?
Let number of paperback copes of novel = x
Then number of hardcover copes of novel = 100 - x
(1) If 20 hardcover versions of this book were sold, there would be three times as many hardcover versions of the book remaining as paperback versions of the book remaining.
Remaining number of hardcover copes of novel = 100 - x - 20 = 80 - x
Assuming that only hardcover were sold than remaining number of paperback = x
Now 3x = 80 - x
x = 20
SUFFICIENT.
(2) If the hardcover version of the book cost twice as much as the paperback version of the book, the total sales of all books in stock would yield $90.
Let cost o hardcover = Ch
Cost o paperback = Cp
and Ch = 2Cp
Now, x * Cp + (100 - x) * Ch = 90
x * Cp + (100 - x) * 2Cp = 90
INSUFFICIENT.
Answer A.
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