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?

Question

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?, 9 5 × 7 50000, 9 4 × 7 50000, 9 5 100000, 9 4 × 3 50000

MARKS App · Accepted Answer

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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