Topic Details (Notes format)

How to Calculate Permutations (Ordered Arrangements)

Subject: Mathematics

Book: Maths Mastery

Permutations count distinct ways to arrange a set of objects where order matters. The formula for the number of permutations of n distinct items taken k at a time is P(n, k) = n! / (n–k)!. For example, the number of ways to arrange 3 items out of 5 is P(5, 3) = 5! / 2! = 60. Permutations arise in tasks like planning seat arrangements, ordering steps in processes, or counting possible password permutations. This concept is key to combinatorial analysis, bridging real-life scenarios where item order is crucial—such as scheduling or competition ranks.

Practice Questions

A number is increased by 20% and then decreased by 20%. What is the net change?

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If the cost price of an item is Rs. 400 and the selling price is Rs. 500, what is the profit percentage?

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If x^2 - 5x + 6 = 0, what are the roots?

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What is the HCF of 72 and 120?

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If a = 4 and b = 5, what is the value of (a+b)^2?

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If a+b = 10 and ab = 21, what is the value of a^3 + b^3?

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What is the LCM of 15 and 20?

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If a number is divisible by 9, it is also divisible by which of the following?

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If x^2 + 4x + 4 = 0, what is the value of x?

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If x:y = 2:3 and z:y = 4:3, what is x:z?

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