Section: Mathematics Usage

1) John currently has enough money to buy 45 books. If the cost of each book was 10 cents less, John could buy 5 more books. How much money does John have to spend on books?

1. $40
2. $45
3. $50
4. $75
5. $100

Let c = cost of each book. Let m = total money. Thus m = 45c and m = 50(c - 10).

Therefore 45c = 50(c - 10)
45c = 50c - 500
500 = 5c
100 = c

Thus m = 4500 cents or $45.