Understanding Basics: Permutations and Combinations

# Understanding Basics: Permutations and Combinations Video Lecture | Quantitative Aptitude for SSC CGL

## Quantitative Aptitude for SSC CGL

314 videos|170 docs|185 tests

## FAQs on Understanding Basics: Permutations and Combinations Video Lecture - Quantitative Aptitude for SSC CGL

 1. What is the difference between permutations and combinations?
Ans. Permutations and combinations are both mathematical concepts used to count the number of ways to arrange or select items. The main difference is that permutations consider the order of the items, while combinations do not. In permutations, the order matters, so for example, ABC is considered different from BAC or CAB. In combinations, the order does not matter, so ABC, BAC, and CAB are all considered the same combination.
 2. How do I calculate the number of permutations?
Ans. To calculate the number of permutations, you need to multiply the number of choices for each position. For example, if you have 5 items and you want to arrange them in a specific order, you would start with 5 choices for the first position, then 4 choices for the second position, 3 choices for the third position, and so on. The number of permutations would be 5 x 4 x 3 x 2 x 1 = 120.
 3. How do I calculate the number of combinations?
Ans. To calculate the number of combinations, you can use the formula nCr, where n represents the total number of items and r represents the number of items being selected. The formula is n! / (r!(n-r)!), where ! denotes factorial. For example, if you have 5 items and you want to select 3 of them, the number of combinations would be 5! / (3!(5-3)!) = 10.
 4. Can permutations and combinations be used in real-life situations?
Ans. Yes, permutations and combinations have various applications in real-life situations. For example, permutations can be used to calculate the number of possible outcomes in a lottery draw or the number of ways to arrange a group of people in a line. Combinations can be used to calculate the number of possible combinations of ingredients in a recipe or the number of ways to select a committee from a larger group of people.
 5. Are there any shortcuts or tricks to solve permutations and combinations problems?
Ans. Yes, there are some shortcuts and tricks that can be used to solve permutations and combinations problems more efficiently. For example, if you have to find the number of permutations of a set of items where some items are repeated, you can divide the total number of permutations by the factorial of the number of times each item is repeated. Similarly, for combinations, you can use the Pascal's triangle or the combination formula directly to calculate the number of combinations.

## Quantitative Aptitude for SSC CGL

314 videos|170 docs|185 tests

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