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

If a:b = 7:9 and b:c = 5:6, what is a:c?

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What is the area of an equilateral triangle with side length 10 cm?

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If x + 1/x = 5, what is the value of x^2 + 1/x^2?

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What is the square root of 121?

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What is the probability of drawing a king from a standard deck of 52 playing cards?

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

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If the sides of a triangle are 6 cm, 8 cm, and 10 cm, what is the area of the triangle?

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What is the sum of all even numbers between 1 and 50?

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What is the area of a circle with a diameter of 14 cm?

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The area of an equilateral triangle with side length 6 cm is:

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