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

If a+b = 10 and ab = 21, what is the value of (a-b)^2?

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If sin(θ) = 0.6 and θ is acute, what is cos(θ)?

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A rectangle has an area of 48 cm² and a length of 8 cm. What is its width?

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If the average of five consecutive odd numbers is 25, what is the largest number?

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If the length of a rectangle is doubled and the width is halved, what is the change in area?

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