Question
Given a set of n rays in a plane, define a reversal as the operation of reversing precisely one ray and obtaining a new set of rays. If all the rays are reversed after 42 operations, then n can be
Answer: Option D
:
D
For a ray to get back to its original orientation, it requires an even no. of operations. Since, all the rays get reversed after 42 operations and if there are k rays ⇒ 2n+k = 42 ⇒ k has to be even. Hence, choice (d) is the right answer
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:
D
For a ray to get back to its original orientation, it requires an even no. of operations. Since, all the rays get reversed after 42 operations and if there are k rays ⇒ 2n+k = 42 ⇒ k has to be even. Hence, choice (d) is the right answer
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