Q. 285.0( 3 Votes )

# Five persons entered the lift cabin on the ground floor of an 8 floored house. Suppose that each of them independently and with equal probability can leave the cabin at any floor beginning with the first, then the probability of all 5 persons leaving at different floor is

A.

B.

C.

D.

Answer :

As building has 8 floors including ground.

So, they have 7 options to leave the lift.

∴ total ways in which persons can leave the lift = 7^{5}

As the number of ways in which all persons leave in a different floor can be given by: 7× 6× 5× 4× 3 = ^{7}P_{5}

∴ P(that all leave lift in different floor) =

Our answer matches with option (a)

∴ Option (a) is the only correct choice

Rate this question :

A natural number is chosen at random from amongst first 500. What is the probability that the number so chosen is divisible by 3 or 5?

RD Sharma - MathematicsIn a single throw of two dice, find the probability that neither a doublet nor a total of 9 will appear.

RD Sharma - MathematicsOne of the two events must happen. Given that the chance of one is two-third of the other, find the odds in favour of the other.

RD Sharma - MathematicsA card is drawn at random from a well-shuffled deck of 52 cards. Find the probability of its being a spade or a king.

RD Sharma - MathematicsOne of the two events must occur. If the chance of one is 2/3 of the other, then odds in favour of the other are

RD Sharma - MathematicsThe probability that a person will travel by plane is 3/5 and that he will travel by train is 1/4. What is the probability that he (she) will travel by plane or train?

RD Sharma - MathematicsIf the probability for A to fail in an examination is 0.2 and that for B is 0.3, then the probability that either A or B fails is

RD Sharma - Mathematics