Question

The hardcover version of a book sells for 15 dollars and the paperback sells for 11.50. If a store sells 70 copies of the book in one month and charges 917 dollars how many hardcover versions were sold

Answer 1

Answer: 32 copies of hardcover version.

Step-by-step explanation: Suppose the quantity of hardcover version copies sold is H and the paperback copies is P.

1) A store sells a total of 70 copies:

H + P = 70

2) One hardcover is sold for $15 and one paperback for $11.50. In one month was charged $917:

15H + 11.5P = 917

Solving the system of equations:

H + P = 70 (I)

15H + 11.5P = 917 (II)

Since it is asked for the hardcover version, find H.

Multiply equation (I) by -11.5:

-11.5H - 11.5P = - 805 (III)

Add (II) and (III):

-11.5H - 11.5P = - 805

  15H + 11.5P = 917

  3.5H            = 112

H = 32

In one month, it was sold 32 hardcover version of a book.