An examination paper has 150 multiple-choice questions of one mark each, with each question having four choices. Each incorrect answer fetches -0.25 mark. Suppose 1000 students choose all their answers randomly with uniform probability. The sum total of the expected marks obtained by all these students is:
(A) 0
(B) 2550
(C) 7525
(D) 9375
Answer: (D)
Explanation:
Expected marks per question is = -0.25 * 3/4 + 1 * 1/4 = 1/16 Since choice is uniformly distributed, expected marks = 150*1000/16 = 9375