Mark (√) against the correct answer in each of the following:
The probability of the safe arrival of one ship out of 5 is 
. What is the probability of the safe arrival of at least 3 ships?
The probability of safe arrival of the ship is 1/5
Using Bernoulli’s Trial we have,
P(Success=x) = nCx.px.q(n-x)
x=0, 1, 2, ………n and q = (1-p), n =5
p = 1/5 , q = 4/5
Probability of safe arrival of at least 3 ships is =
P(3)+P(4)+P(5)
⇒ 5C3(
)3(
)2+5C4(
)4(
)1+5C5(
)5(
)0
⇒ 
1