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AP EAMCET202023 Sep 2020Morning ShiftMathematicsProbabilityActual

If on an average 9 mountain climbers out of 10 return safely, what is the probability that with 5 climbers out, at least 4 will return safely?

Options

  1. A9 5 × 7 50000
  2. B9 4 × 7 50000
  3. C9 5 100000
  4. D9 4 × 3 50000

Correct answer

B. 9 4 × 7 50000

Step-by-step solution

P ( returning safely ) = 9 10 P ( at least 4 returning safely ) + P ( 5 returning safely ) = C 4 5 · 9 10 4 · 1 10 1 + C 5 5 · 9 10 5 = 5 · 9 4 10 5 + 9 5 10 5 = 9 4 ( 14 ) 10 5 = 9 4 · 7 50000

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