unit-7-permutations-and-combinations

Unit-7 Permutations and Combinations

In this unit you will study about the Multiplication principle, permutations, combinations and Binomial Theorem.

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Suppose you have a suitcase with a combination lock that can be unlocked by setting the three numbers of the combination correctly(The numbers can be 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9). If you forget your combination, but remember that all the digits are less than 5 and none of the digits are repeated, what is the maximum number of combinations you may have to try till you get the correct combination?

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Learning Pundits Content Team

Written on Apr 23, 2019 12:21:06 PM

Let’s find out how many combinations are possible subject to the conditions that all the three digits are distinct and less than 5. Here there are 6 digits 0, 1, 2, 3, 4 and 5 which are to be distributed to 3 places. This can be done in P(6, 3) = 6 × 5 × 4 = 120 ways. So, we may have to try at least 120 different combinations. This is of course the worst possible. If we are lucky, we may get the correct number the first time itself!