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JEE Main Mathematics question

MathematicsPermutations and CombinationsJEE Main

Let be the number of ways in which boys and girls can stand in a queue in such a way that all the girls stand consecutively in the queue. Let be the number of ways in which boys and girls can stand in a queue in such a way that exactly four girls stand consecutively in the queue. Then the value of is

Answer: 5

Solution

All girls together: treat the girls as one block, so the block and boys arrange in ways and the girls inside in ways: . Exactly four girls together: arrange the boys in ways, making gaps; put a run of

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Question ID VK-020848