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Class 11MathematicsPermutations and CombinationsFundamental principle of countingExpert
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In a (5)-slot lock, each slot contains a number from (1) to (4). At least one slot must contain (4). How many locks are possible?

Answer and explanation

Correct answer: (4^5-3^5=781)

For at least one (4), subtract the (3^5) arrangements with no (4) from all (4^5). The complement method is easy for at-least questions.

Related tags

CountingLockAt-Least-OneFundamental Principle Of CountingPermutations And CombinationsMathematicsClass 11 Mcq
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