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 7th term of the arithmetic progression 3, 6, 9, 12,...?

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What is the square root of 144?

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A square is inscribed in a circle with a radius of 5 cm. What is the area of the square?

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If a cone has a base radius of 3 cm and height of 4 cm, what is its slant height?

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If two complementary angles differ by 30°, what are the angles?

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If the perimeter of a square is 40 cm, what is the area of the square?

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If 8x = 512, what is the value of x?

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If a right triangle has legs of 9 cm and 12 cm, what is the length of the hypotenuse?

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What is the greatest common divisor (GCD) of 36 and 48?

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