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Question
We wish to select 6 persons from 8, but if the person A is chosen, then B must be chosen. In how many ways can the selection be made?
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Solution
6 people are to be selected from 8.
There are two case.
(i) When A is selected, then B must be chosen.
∴\[\text{Number of ways} = {}^6 C_4 = 15\]
(ii) When A is not chosen:
∴ Total number of ways = 15 + 7 = 22
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