Question
Five different pens out of which 2 are red and the rest
are blue are to be arranged in a line. Find the number of ways in which the two red pens are not placed together.Solution
Total number of ways to arrange 5 pens = 5! = 120 ways
If we consider 2 red pens as one item, number of arrangements = 2! = 2 ways
Number of arrangements of remaining 4 items = 4! = 24 ways
Therefore, required number of ways = 120 – (2 × 24) = 72 ways
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