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Probability

Six persons t...

Question

Six persons try to swim across a wide river. It is known that on an average, only three persons out of the ten are successful in crossing the river. What is the probability that at most four of the six persons will cross river safely?

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Solution

$P (c r o s s i n g t h e r i v e r) = 0.3 P (a t m o s t 4 w i l l c r o s s) = 1 - P (5 o r 6 c r o s s e d s a f e l y) P = 1 - {0.3}^{5} (0.7 + 0.3) = 1 - 0.00243 P = 0.99757$

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