EASY
Earn 100

In an International tennis tournament, the odds that player John will be champion is 4 to 3 and the odds that player Steve will be champion is 1 to 4. The odds that either  John or Steve will become the champion is:

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Important Questions on Probability

HARD
If a 3-digit number is randomly chosen. What is the probability that either the number itself or some permutation of the number (which is a 3-digit number) is divisible by 4 and 5?
EASY
An ellipse of eccentricity 223 is inscribed in a circle. A point is chosen inside the circle at random. The probability that the point lies outside the ellipse is
MEDIUM
A letter is taken at random from the word "STATISTICS" and another letter is taken at random from the word "ASSISTANT". The probability that they are same letters is
HARD

If 12 identical balls are to be placed in 3 identical boxes, then the probability that one of the boxes contains exactly 3 balls is

EASY
The probability that among 7 persons, no 2 were born on the same day of a week is
HARD
Let Xn=1, 2, 3,.,n and let a subset A of Xn be chosen so that every pair of elements of A differ by at least 3. (For example, if n=5, A can be , 2 or 1,5 Among others). When n=10, let the probability that 1A be p and let the probability that 2A be q. Then-
MEDIUM
Let a and b be 2 consecutive integers selected from the first 20 natural numbers. The probability that a2+b2+a2b2 is an odd positive integer is
MEDIUM
A box contains coupons labelled 1, 2, ...., 100. Five coupons are picked at random one after another without replacement. Let the numbers on the coupons be x1,x2,., x5 . What is the probability that x1>x2>x3 and x3<x4<x5 ?
HARD
Two different families A and B are blessed with equal number of children. There are 3 tickets to be distributed amongst the children of these families so that no child gets more than one ticket. If the probability that all the tickets go to the children of the family B is 112, then the number of children in each family is
HARD
If two different numbers are taken from the set 0, 1, 2, 3,....., 10; then the probability that their sum as well as absolute difference are both multiple of 4, is:
HARD
An urn contains marbles of four colours : red, white, blue and green. When four marbles are drawn without replacement, the following events are equally likely:

(i) The selection of four red marbles

(ii) The selection of one white and three red marbles

(iii) The selection of one white, one blue and two red marbles

(iv) The selection of one marble of each colour

The smallest total number of marbles satisfying the given condition is
HARD
Let X be a set containing 10 elements and PX be its power set. If A and B are picked up at random from PX, with replacement, then the probability that A and B have equal number of elements is:
HARD
There are 6 boxes labelled B1, B2,.,B6. In each trial, two fair dice D1,D2 are thrown. If D1 shows j and D2 shows k, then j balls are put into the box Bk. After n trials, what is the probability that B1 contains at most one ball?
HARD
From a group of 10 men and 5 women, four member committees are to be formed each of which must contain at least one women. Then the probability for these committees to have more women than men, is :
HARD
A box contains coupons labeled 1, 2, 3 ..... n . A coupon is picked at random and the number x is noted. The coupon is put back into the box and a new coupon is picked at random. The number is y . Then the probability that one of the numbers x, y divides the other is (in the options below r denotes the largest integer less than or equal to r )
MEDIUM
A determinant of second order is made with the elements 0, 1. What is the probability that the determinant is positive?
HARD
Choose a number n uniformly at random from the set 1,2,3,.....,99,100. Choose one of the first seven days of the year 2014 at random and consider n consecutive days starting from the chosen day. What is the probability that among the chosen n days, the number of Sundays is different from the number of Mondays?
MEDIUM
A quadratic equation ax2+bx+c=0   with distinct coefficients is formed. It a,b,c are chosen from the numbers 2,3 and 5, then the probability that the equation has real roots is
HARD
If the lengths of the sides of a triangle are decided by the three throws of a single fair die, then the probability that the triangle is of maximum area given that it is an isosceles triangle, is:
HARD
A multiple choice examination has 5 questions. Each question has three alternative answers out of which exactly one is correct. The probability that a student will get 4 or more correct answers just by guessing is :