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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? - Mathematics

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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:

\[\text{Number of ways} =^7 C_6 = 7\]

∴ Total number of ways = 15 + 7 = 22

Concept: Combination
  Is there an error in this question or solution?

APPEARS IN

RD Sharma Class 11 Mathematics Textbook
Chapter 17 Combinations
Exercise 17.2 | Q 23 | Page 16

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