Question
From 6 different novels and 3 different dictionaries, 4 novels and 1 dictionary are to be selected and arranged in a row on a shelf so that the dictionary is always in the middle. Then the number of such arrangements is
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less than 500
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at least 500 but less than 750
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at least 750 but less than 1000
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at least 1000
Solution
D.
at least 1000
N1N2N3 – N6, D1D2D3
The number of ways = 6c4 × 3c1 × 24
= 15 × 3 × 24 = 1080
