Question

There are four machines and it is know that exactly two of them are faulty. They are tested, one by one, in a random order till both the faulty machines are indentified. Then the probability that only two tests are needed is

Solution

Correct option is

A = event that two defective machines are indentified in first two tests out of four machines.  

             

SIMILAR QUESTIONS

Q1

A person draws a card from a pack of playing card, replaces it and shuffles the pack. He continues doing this until he shows a spade. The chance that he will fail the first two times is  

Q2

The probability that in toss of two dice we obtain the sum 7 and 11 is

Q3

Two cards are draw at random from a pack of 52 cards. The probability of these two being aces is

Q4

An urn contains 3 white and 5 black balls. One ball is draw. What is the probability that it is black?

Q5

Forms a pack of 52 cards, four cards are drawn. Find the chance that they will be the four honours of the same suit.

Q6

If a coin tossed 15 times, what is the probability of getting head as many times in the first ten throws as in the last five?

Q7

A person throws two dice, one the common cube and the other a regular tetrahedron, the number on the lowest face being taken in the case of the tetrahedron. What is the chance that the sum of the number thrown is not less five?

Q8

The card are draw successively with replacement from a well shuffled deck of 52 cards. The probability of drawing two aces is

Q9

The chance of throwing an ace is the first only of two successive thrown with an ordinary die is