Answer:
15,120 for the first question. 1,680 if one of the books is a must
Step-by-step explanation:
When Ron chooses his first book, he has 9 options. After that, when he chooses his second book, he only has 8 choices because he already picked one of them. By his third choice, he only has 7 choices and so on.
We can make an equation to represent this,
9 x 8 x 7 x 6 x 5
Multiplying all of that out gets you 15,120.
The second problem is even easier. Since one of the books is already chosen for him, he starts off only having 8 options. Since he is only choosing four books this time, we are only multiplying four numbers.
8 x 7 x 6 x 5
Multiplying all of that out tells you there are 1,680 ways he can make his selection in the second scenario.
