Correct Answer - B
Let p be the probability of success and q that of failure. It given that .
p=2q⇒2q=1-q⇒q=
1
3
and=
2
3
Let X denote the number of successes in 6 trails. Then, ltbgt P(X=r)=.6Crprq6-r=.6Cr(
2
3
)r(
1
3
)6-r,r=0,2,.......6
Required Probability =P(X≥5)=P(X=5)+P(X=6)
.6C5(
2
3
)5(
1
3
)6-5+.6C6(
2
3
)6(
1
3
)0=
256
729
.
