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?

A. 9/5 B. 10/7 C. 7/10 D. 5/7

Answer Answer: Option C Explanation: 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

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

A. 9/19 B. 9/38 C. 10/19 D. 5/19

Answer Answer: Option A Explanation: 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

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?

A. 69/91 B. 80/91 C. 21/91 D. 55/91

Answer Answer: Option A Explanation: Total balls = 15
Probability = 11C4/15C4 = 22/91
one is black = 1- 22/91 = 69/91