# Q. 5  An urn contains 25 balls of which 10 balls bear a mark  $'X'$  and the remaining 15 bear a mark $'Y'.$ A ball is drawn at random from the urn, its mark is noted down and it is replaced. If 6 balls are drawn in this way, find the probability that             (iii) at least one ball will bear $'Y'$ mark.

S seema garhwal

$P(atleast\, one\, bear\, \, Y\, mark) =P(Z\geq 1)=1-P(Z=0)$

$=1-(\frac{2}{5})^6$

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