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.

Answers (1)
S seema garhwal


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