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andrey2020 [161]
3 years ago
13

Marco purchased a large box of comic books for $300. He gave 15 of the comic books to his brother and then sold the rest on an i

nternet website for $330 making a profit , making a profit of $1.50 on each one.how many comic books were in the box? what was the original price of each comic book (assuming they all cost the same amount)?​
Mathematics
1 answer:
Yuri [45]3 years ago
5 0

Answer: There are 75 books.

Price of each book = $4.

Step-by-step explanation:

Let x = Number of books in the box.

Then as per given,

Cost of x books = $300

Cost of one book = \$(\dfrac{300}x)

Books left after giving 15 of them = x-15

Selling price of (x-15) books=  $330

Selling price of one book = \$(\dfrac{330}{x-15})

Profit on each book= $1.50

Profit = selling price - cost price

\Rightarrow 1.50=\dfrac{330}{x-15}-\dfrac{300}{x}\\\\\Rightarrow\ 1.50=\dfrac{330(x)-300(x-15)}{x(x-15)}\\\\\Rightarrow\ 1.50=\dfrac{330x-300x+4500}{x^2-15x}\\\\\Rightarrow\ 1.50(x^2-15x)=30x+4500\\\\\Rightarrow\ 1.50x^2-22.5x=30x+4500\\\\\Rightarrow\ 1.50x^2-52.5x-4500=0\\\\\Rightarrow\ 1.50x^2-52.5x-4500=0\\\\\Rightarrow\ x^2-25x-3000=0\ \ [\text{divide by 1.5}]

\Rightarrow (x+40)(x-75)=0\\\\\Rightarrow\ x=-40,75

Number of books cannot be negative.

So, there are 75 books.

Price of each book = \dfrac{300}{75}=\$4

So price of each book = $4.

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