Question

alana and petra go to a used book sale, where every book is the same price. Alana buys 5 books and Petra buys 4 books. They run into their friend Angus, who really loves to read, and discover that he has bought 19 books. Angus received a $10 discount, but he still spent $5 more than Alana and Petra combined. How much does one book cost?

Answer 1

After understanding the problem, formulate equations to determine the unknown. Let x be the price of one book. Equating Alana&Petra's expense with Angus' would be

5x + 4x +5 = 19x - 10

The 5 in the left side is needed because Angus' expense is $5 more. Also, the 10 on the right side represents the $10 discount. Solving the equation,

19x = 9x = 5+10
10x = 15
x = $1.5

Therefore, the book costs $1.5.