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

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The simple interest on Rs. 4000 at 5% per annum for 2 years is:

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If the radius of a circle is 7 cm, what is its circumference?

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What is the sum of the first 20 odd numbers?

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If a rectangle has a length of 10 cm and a width of 6 cm, what is its perimeter?

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

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

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What is the HCF of 48 and 180?

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If 2a + b = 10 and a - b = 4, what is the value of a?

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

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