Multiple choice

Rahul, Rakshita and Gurmeet, working together, would have taken more than 7 days to finish a job. On the other hand, Rahul and Gurmeet, working together would have taken less than 15 days to finish the job. However, they all worked together for 6 days, followed by Rakshita, who worked alone for 3 more days to finish the job. If Rakshita had worked alone on the job, then the number of days she would have taken to finish the job cannot be

  1. 17

  2. 21

  3. 16

  4. 20
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let R, S, G be rates. (R+S+G) > 1/7. (R+G) < 1/15. 6(R+S+G) + 3S = 1. 6(R+G) + 9S = 1. Since R+G < 1/15, 6(R+G) < 6/15 = 0.4. So 9S = 1 - 6(R+G) > 1 - 0.4 = 0.6. S > 0.6/9 = 1/15. S > 0.066. Days = 1/S < 15. The question asks what S cannot be. This requires more complex inequalities.

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