WBJEE · Maths · Probability
An objective type test paper has 5 questions. Out of these 5 questions, 3 questions have four options each \((a, b, c, d)\) with one option being the correct answer. The other 2 questions have two options each, namely true and false. A candidate randomly ticks the options. Then, the probability that he/she will tick the correct option in atleast four questions, is
- A \(\frac{5}{32}\)
- B \(\frac{3}{128}\)
- C \(\frac{3}{256}\)
- D \(\frac{3}{64}\)
Answer & Solution
Correct Answer
(D) \(\frac{3}{64}\)
Step-by-step Solution
Detailed explanation
Total sample space, \(n(S)=4^{3} \cdot 2^{2}\) and total number of favourable cases \[ n(E)=\left({ }^{3} C_{1} \cdot 3+{ }^{2} C_{1} \cdot 1\right)+1 \] \(\therefore\) Required probability \(=\frac{n(E)}{n(S)}\)…
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