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

What is the slope of a line passing through the points (2, 3) and (4, 7)?

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If a cylinder has a radius of 7 cm and height of 10 cm, what is its volume?

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

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What is the HCF of 72 and 120?

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If 3x = 81, what is the value of x?

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If the product of two numbers is 120 and their sum is 26, what are the numbers?

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What is the probability of drawing an ace from a standard deck of 52 cards?

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If the sum of the angles of a polygon is 1080°, how many sides does the polygon have?

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The perimeter of a rectangle is 40 cm, and its length is 12 cm. What is its width?

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If sin(A) = 3/5 and cos(B) = 5/13, where A and B are acute angles, what is sin(A+B)?

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