Destroyer QR 86 and 87

[topdent1]

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What is the difference in these 2 problems? What key word(s) in either problem is the hint that they are different? I know how to do them, its just that they sound so similar that I could mistake one for the other.

 

[enamelion]

Are you talking about the 2006 edition? If so, then both problems involve permutations. In 86, the painter has 9 colors from which to paint 4 rooms. Here, the order with which he paints the rooms matter. For example, if he paints room A blue, he has to paint room B a different color, and so on. You would not use a combination in this case because the order matters. If, however, the question asks how many ways the painter can choose 4 colors from 9 colors, then you would use the formula for combinations. Number 87 uses permutations as well. Here, five people are running for four positions, but the order of the positions is important. This is because each position needs to be filled by only one person. Hope that helped.

 

[klutzy1987]

Dammit people post the question i do not keep a destroyre handy at every second of the day.

 

[topdent1]

nope, its the April 2008 version.

 

[topdent1]

Are you talking about the 2006 edition? If so, then both problems involve permutations. In 86, the painter has 9 colors from which to paint 4 rooms. Here, the order with which he paints the rooms matter. For example, if he paints room A blue, he has to paint room B a different color, and so on. You would not use a combination in this case because the order matters. If, however, the question asks how many ways the painter can choose 4 colors from 9 colors, then you would use the formula for combinations. Number 87 uses permutations as well. Here, five people are running for four positions, but the order of the positions is important. This is because each position needs to be filled by only one person. Hope that helped.

Ah...I just read the rest of your post and its the same question. Good explanation.

 

[boxdesker]

Why can't the painter paint each room the same color, making it 9^4?

You know why? Because Destroyer is pretty bad at QR questions.

 

[gentile1225]

i think this is a misprint. 86 should be 9^4, and 87 is 6P4.

 

[klutzy1987]

Why can't the painter paint each room the same color, making it 9^4?

You know why? Because Destroyer is pretty bad at QR questions.

The QR is actually pretty good however alot of the probability questions are poorly worded. Eventually im sure these will be fixed. The question is not a mistake it just doesnt specify what exactly it is asking and leaves alot of room open for different answers.