Question

A book store earned $235 in sales for 4 copies of a new cookbook and 5 copies of a new science fiction novel. The next day it earned $180 in sales for 3 copies of the cookbook and 4 copies of the science fiction novel. What was the price of each book?

Answer 1

The cost of a cookbook is $40 and the cost of a science fiction book is $15.

Explanation:

Given,

4 copies of cookbook and 5 copies of science fiction cost $235.

3 copies of cookbook and 4 copies of science fiction cost $180.

To find the cost of each cookbook and science fiction book.

Let us take

The cost of each cookbook is = x

The cost of each science fiction = y

According to the problem,

4x+5y = 235 ---- (1)

3x+4y = 180 ----- (2)

Multipy (1) by 3 and (2) by 4 and the subtract

(12x+15y) - (12x+16y) = 705 - 720

or, -y = - 15

or, y = 15

Now, putting the value of y in (1) we get,

4x = 235 -(5×15)

or, 4x = 160

or, x = 40

Hence,

The cost of a cookbook is $40 and the cost of a science fiction book is $15.