At the back of a bookstore, there is a storeroom where multiple copies of three types of books are kept. There are copies of a novel, an autobiography, and a linear algebra textbook. Each copy of the novel is 1cm thick, each copy of the autobiography is also 1cm thick while the linear algebra textbook is 2cm thick. Determine the number of ways to have a stack of books that is 5 cm high.

Guest May 4, 2020

#1**+1 **

Here's what I get :

( 1, 1 , 2)

5(1) = 5 novels

5(1) = 5 autos

4(1)+ 1(1) = 4 novels + 1 auto

4(1) + 1(1) = 4 autos + 1 novel

3(1) + 1(2) = 3 novels + 1 linear

3(1) + 1(2) = 3 autos + 1 linear

2(2) + 1(1) = 2 linear + 1 novel

2(2) + 1(1) = 2 linear + 1 auto

1(2) + 3(1) = 1 linear + 3 novels

1(2) + 3(1) = 1 linear + 3 autos

2(1) + 1(1) + 1(2) = 2 novels + 1 auto + 1 linear

2(1) + 1(1) + 1(2) = 2 auto + 1 novel + 1 linear

Did I miss any ????

CPhill May 4, 2020