Expert: Lynn Houston - 5/28/2009

Question
A certain used-book dealer sells paperback books at 3 times dealer's cost and hardbacks books at 4 times dealer's cost.Last week the dealer sold a total of 120 books, each of which had cost the dealer $1. I the gross profit(sales revenue minus dealer's cost) on the sale of all these books was $300, how ,many of the books sold were paperbacks?

Answer
Let h = hardback books and p = paperback books

h + p = 120
(3h-h)+ (4p-p) = 300

h=120-p

2(120-p) + 3p = 300
240 - 2p + 3p = 300
p = 60, therefore
h = 60

He bought 60 hardbacks and 60 paperbacks for a total of $120.  He sold 60 @ $4 = 240 and 60 @$3 = 180 for a total of $420, minus his cost = $300

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