From this collection of books, Diane will choose without looking three hardcover detective novels to read during a school break. How many combinations of the three books are possible? Explain
Number of combinations: ?
I'm assuming that the books are arranged on separate shelves, so that Diane knows exactly what books she is choosing. If that is correct, then she can choose in: 12C3 = 220 different ways of choosing 3 hardcover detective novels.