1. ## Probabilty: Some Answers That Need Checking Part 3

Hi,

If anyone can please check what I have done, that would be awesome,

48. Music: You want to purchase three CDs from an online collection that contains the types of music shown below. You want each CD to contain a different type of music such that two CDs are different types of contemporary music, and one CD is a type of classical music. How many sets of music types can you choose?

Types of Music:

Contemporary:

-Jazz
-Country
-Blues
-Rap
-Rock & Roll

Classical:

-Opera
-Concerts
-Symphony

Is the answer to this, 8npr8(permutation)? That would make the answer, 4,320, and that doesn't seem right to me, but for some reason I just have a gut feeling about it. I wouldn't be able to tell you how I arrived at such a conjecture, but for some reason I feel that it's right.

50. Arcade Games: An arcade has 20 different arcade games. You want to play at least 14 of them. How many different combinations of arcade games can you play? 20nCr= 38,760. There are 38,760 combinations of arcade games you can play.

I think that that's wrong, and that that is way too many combinations of arcade games.

52.Extended Response: A group of fifteen high school students is volunteering at a local fire station. Of these students, five will be assigned to wash fire trucks, seven will be assigned to repaint the station’s interior, and three will be assigned to do maintenance on the station’s exterior.

a) Calculate: One way to count the number of possible job assignments is to find the number of permutations of 5W’s(for wash) 7R’s(for repainting) and three M’s(for maintenance. Use this method to write the number of possible job assignments first as an expression involving factorials, and then as a number.
b) Calculate: Another way to count the number of possible job assignments is to first choose the 5W’s, then the 7R’s, and then the three 3M’s. Use this method to write the number of possible job assignments first as an expression involving factorials, and then as a number.
c) Analyze: Compare your results from parts a and b, and explain why they make sense.

I know the answer to part c is that the answers to parts a and b are the same, and that that is why they make sense, but otherwise I'm stuck.

Thank you very much
Isabel