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 sum of the first 50 positive integers?

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What is the value of log₃(27)?

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

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If the sum of three consecutive integers is 96, what are the integers?

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If a+b = 10 and ab = 21, what is the value of a^3 + b^3?

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If sin(A) = 1/2 and A is acute, what is the value of A?

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The sides of a triangle are 5 cm, 12 cm, and 13 cm. What type of triangle is it?

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

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If the ratio of two numbers is 3:5 and their HCF is 4, what are the numbers?

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