1.  In a collage 10% of students speaking english, 70% speaking hindhi 10% speaking both. If a student selected at random, What is the probability of the students who speak english or hindhi?


9/5
10/7
7/10
5/7


Answer

 Option

P(a) = 10/100 = 1/10 P(b) = 70/100 = 7/10 P (both) = 10/100 = 1/10 P (a * b) = (1+7-1) /10 = 7/10

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2.  A box contains 10 black and 10 white marbles. The probability of drawing two marbles of the same colour is?


9/19
9/38
10/19
5/19


Answer

 Option

Total number of balls =20. Let S be the sample space. Then, n(S) = Number of ways of drawing 2 balls out of 20 = 20C2 = (20*19)/(2*1) = 190 Let E = event of drawing 2 balls of the same colour n(E) = (10C2 + 10C2) = 2*(10*9/2*1) = 90 Therefore P(E) = n(E)/n(S) = 90/190 = 9/19

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3.  P and Q throw a dice. Find the probability that P's throw is not greater than Q' s through


7/5
12/5
7/12
7/11


Answer

 Option

A B 1 1 2 3 4 5 6 2 2 3 4 5 6 3 3 4 5 6 4 4 5 6 5 5 6 6 6 n(E) = 21 n(S) = 36 P = 21/36 = 7/12

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4.  P and Q throw a dice. Find the probability that P's throw is not greater than Q's through?


7/5
12/7
7/12
7/11


Answer

 Option

A B 1 1 2 3 4 5 6 2 2 3 4 5 6 3 3 4 5 6 4 4 5 6 5 5 6 6 6 n(E) = 21 n(S) = 36 P = 21/36 = 7/12

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5.  A basket contains 6 white 4 black 2 pink and 3 green marbles. If four marbles are picked at random, What is the probability that atleast one is black?


69/91
80/91
21/91
55/91


Answer

 Option

Total balls = 15 Probability = 11C4/15C4 = 22/91 one is black = 1- 22/91 = 69/91

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