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In how many ways can I invite one or more of six friends to a dinner? |
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Answer» He can invite one or more friends by inviting 1 friend, or 2 friends or 3 friends, or all the 6 friends. 1 friend can be selected out of 6 in 6C1 = 6 ways 2 friends can be selected out of 6 in 6C2 = 15 ways 3 friends can be selected out of 6 in 6C3 = 20 ways 4 friends can be selected out of 6 in 6C4 = 15 ways 5 friends can be selected out of 6 in 6C5 = 6 ways 6 friends can be selected out of 6 in 6C6 = 1 ways Therefore the required number of ways (combinations) = 6 + 15 + 20 + 15 + 6 + 1 = 63 |
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