CAT 2021 Permutations and Combinations Question (Hard)

Question

The number of groups of three or more distinct numbers that can be chosen from 1, 2, 3, 4, 5, 6, 7 and 8 so that the groups always include 3 and 5, while 7 and 8 are never included together is

Accepted Answer

Step 1 We are given the set 1, 2, 3, 4, 5, 6, 7, 8 We are to form groups of size 3 that - Always include 3 and 5 - Never include both 7 and 8 together So, 3 and 5 are mandatory in every group. That means we only need to select additional elements from 1, 2, 4, 6, 7, 8 6 elements in total Let s count

CAT 2021

Quantitative

Permutations and Combinations

Hard

The number of groups of three or more distinct numbers that can be chosen from 1, 2, 3, 4, 5, 6, 7 and 8 so that the groups always include 3 and 5, while 7 and 8 are never included together is

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