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 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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The sum of the reciprocals of two numbers is 1/4. If one number is 12, what is the other?

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A cone has a base radius of 7 cm and height of 24 cm. What is its volume?

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What is the square root of 0.25?

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The sum of the squares of two consecutive integers is 145. What are the integers?

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A train 150 m long passes a pole in 15 seconds. What is its speed?

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