Text Solution
Answer : 360
Solution : 1st person can be seated in 6 ways , 2nd person in 5 ways, 3rd person in 4 ways and 4th person in 3 ways. <br> Required number of ways `=(6xx5xx4xx3)=360.`
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in how many different ways can 4 persons be seated in a consecutive row of seven seats??
7 position 4 = P(7,4) = 7�6�5�4 = 840
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2. a shelf contain 5 red books, 4 blue books, and 3 green books. how many different orders can they be arranged if all books of the same color must kept together?First, there are P(3,3) = 3! ways we can choose the order of colors,
that is, (Red,Blue,Green), (Red,Green,Blue), (Blue, Red,Green),
(Blue,Green,Red), (Green,Red,Blue), (Green,Blue,Red)
Then for each of those 3! ways, there are P(5,5) = 5! ways to arrange the 5
red books, P(4,4) = 4! ways to arrange the blue books, and P(3,3) = 3! ways
to arrange the green books.
Answer 3!�5!�4!�3! = 6�120�24�6 = 103,680 ways.
Edwin