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There are four bus routes between A and B; and three bus routes between B and C. A man can travel round-trip in number of ways by bus from A to C via B. If he does not want to use a bus route

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Question

There are four bus routes between A and B; and three bus routes between B and C. A man can travel round-trip in number of ways by bus from A to C via B. If he does not want to use a bus route more than once, in how many ways can he make round trip?

Options

  • 72

  • 144

  • 14

  • 19

MCQ
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Solution

72

Explanation:

In the following figure:

There are 4 bus routes from A to B and 3 routes from B to C.

Therefore, there are 4 × 3 = 12 ways to go from A to C.

It is round trip so the man will travel back from C to A via B.

It is restricted that man can not use same bus routes from C to B and B to A more than once.

Thus, there are 2 × 3 = 6 routes for return journey.

Therefore, the required number of ways = 12 × 6 = 72.

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Chapter 7: Permutations and Combinations - Solved Examples [Page 120]

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NCERT Exemplar Mathematics Exemplar [English] Class 11
Chapter 7 Permutations and Combinations
Solved Examples | Q 13 | Page 120

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