Topic Details (Notes format)

How to Calculate Combinations (Unordered Selections)

Subject: Mathematics

Book: Maths Mastery

Combinations focus on ways to choose k items out of n without regard to order, calculated as C(n, k) = n! / [k!(n–k)!]. For instance, to find the number of ways to select 2 fruits from {Apple, Banana, Cherry}, you have 3 choices: AB, AC, BC, which is C(3, 2) = 3. Combinations appear in scenarios like forming committees, picking lottery numbers, or combining flavors in recipes. Understanding the difference between permutations and combinations clarifies everything from business inventory groupings to advanced probability, ensuring a robust combinatorial foundation.

Practice Questions

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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What is the sum of the first 50 positive integers?

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What is the value of log₃(27)?

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If 2x - 3 = 7, what is the value of x?

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

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If log(100) = 2 and log(10) = 1, what is log(1000)?

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What is the LCM of 15 and 20?

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What is the square root of 0.25?

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If the radius of a circle is doubled, what happens to its area?

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