Question

In one day, a book store earned $191 in sales for 4 copies of a new cookbook and 5 copies of a new science fiction novel. On the next day, it earned $148 in sales for 3 copies of the cookbook and 4 copies of the science fiction novel. What was the price of each book?cookbook $novel $

Answer 1

Case: System of equations

Method:

Let cookbooks be 'c'

and science fiction novel be 's'

$191 in sales for 4 copies of a new cookbook and 5 copies of a new science fiction novel.

191 = 4c + 5s

$148 in sales for 3 copies of the cookbook and 4 copies of the science fiction novel

148 = 3c + 4s

`\begin{gathered} 191=4c+5s....(1)*3 \\ 148=3c+4s.....(2)*4 \\ 573=12c+15s..(1) \\ 592=12c+16s..(2) \\ (2)-(1) \\ 592-573=16s-15s \\ s=19 \end{gathered}`

Plug s = 19 in eqn (1)

191 = 4c + 5s

191 = 4c + 5(19)

191 = 4c +95

4c = 191 - 95

4c = 96

c = 96/4

c =24

Final answer:

Cookbook $24

Novel $19