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 5x - 2 = 13, what is the value of x?

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If a:b = 5:7 and b:c = 6:11, what is a:c?

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If a:b = 2:3 and b:c = 4:5, what is a:c?

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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 - y = 5 and x + y = 15, what is the value of x?

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What is the greatest common divisor (GCD) of 36 and 48?

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What is the sum of all odd numbers from 1 to 99?

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What is the length of the diagonal of a square with a side length of 7 cm?

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If the perimeter of a square is 40 cm, what is the area of the square?

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A sum triples in 20 years at simple interest. What is the rate of interest per annum?

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