If a student randomly guesses five multiple-choice questions, each with five possible choices, what is the probability of getting exactly two correct?
- 128/625 (20.48%)
- 64/625 (10.24%)
- 256/625 (40.96%)
- None of these
Explanation
n = 5 questions
k = 2 correct
p = 1/5 = 0.2 probability correct
q = 4/5 = 0.8 probability wrong
Formula: P = C(n,k) _ p^k _ q^(n-k)
P = C(5,2) _ (0.2)^2 _ (0.8)^3
P = 10 _ 0.04 _ 0.512
P = 0.2048
So probability of getting exactly 2 correct = 0.2048 = 128/625 (20.48%)
Last verified on 11-07-2026
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- 128/625 (20.48%)
- 64/625 (10.24%)
- 256/625 (40.96%)
- None of these
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