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Curated by: Khan Academy India - English (21 videos)
In this video, we use the concept of AND and OR to solve problems involving rearrangement of digits. We discuss both scenarios: repetition allowed and not allowed. For the first scenario, we take 5 digits and try to create as many 3 digit numbers as possible using these digits. Since the repetition is not allowed, we realise that we get different number of ways to perform individual tasks. This is not the case for the second problem discussed where the repetition is allowed. Courses on Khan Academy are always 100% free. Start practicing—and saving your progress—now! (https://www.khanacademy.org/math/ncert-class-11/xea4762213f311c5e:permutations-and-combinations-ncert-new/xea4762213f311c5e:untitled-900/e/permutations_1) Timestamps: 00:00 Problem 1 (3 digit number, repetition not allowed) 00:55 Refresher (Fundamental principle of counting) 01:55 Exploring possibilities (plugging values) 03:00 Setting up the solution (AND and OR) 04:04 Solution (replacing AND with multiplication) 04:38 Visualising all possible 3 digit numbers 04:55 Problem 2 (3 digit number, repetition allowed) 05:30 Setting up (leveraging AND and OR) 06:12 Solution (replacing AND with multiplication) 06:33 Visualising all possible 3 digit numbers Khan Academy India is a nonprofit organization with the mission of providing a free, world-class education for anyone, anywhere. We have videos and exercises that have been translated into multiple Indian languages, and 15 million people around the globe learn on Khan Academy every month. Support Us: https://india.khanacademy.org/donate Created by Ashish Gupta