ProbabilityMCQPYQ Nov. 20Question 3268 of 187
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When two coins are tossed simultaneously the probability of getting at least one tail?

Options

A1
B0.75
C0.5
D0.25
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Correct Answer

✅ Option b — 0.75

All Options:

  • A1
  • B0.75
  • C0.5
  • D0.25

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Detailed Solution & Explanation

**Two Coins Tossed — At Least One Tail** Sample space when two coins are tossed: S={HH,HT,TH,TT}\displaystyle S = \{HH, HT, TH, TT\}, so ∣S∣=4\displaystyle |S| = 4 Favorable outcomes (at least one tail): {HT,TH,TT}\displaystyle \{HT, TH, TT\} → 3 outcomes P(at least one tail)=34=0.75P(\text{at least one tail}) = \frac{3}{4} = 0.75 **Using complement:** P(at least one tail)=1−P(no tail)=1−P(HH)=1−14=34=0.75P(\text{at least one tail}) = 1 - P(\text{no tail}) = 1 - P(HH) = 1 - \frac{1}{4} = \frac{3}{4} = 0.75 Hence, **Option B** is the correct answer.

About This Chapter: Probability

Paper

Paper 3: Quantitative Aptitude

Weightage

5-7 Marks

Key Topics

Probability Operations, Expected Value

A logic-heavy chapter dealing with random experiments, events (mutually exclusive, exhaustive), set theory probability, conditional probability, and Bayes' Theorem. It forms the basis for Theoretical Distributions.

View Official ICAI Syllabus

Exam Strategy Tip

Always draw a quick Venn Diagram or tree when faced with 'At least one' or 'Only A but not B' wording. It saves you from double-counting.

Key Concepts to Understand

Probability

A numerical measure of the likelihood of an event occurring, expressed as a number between 0 (impossible) and 1 (certain). Formula: P(A) = Number of favorable outcomes / Total number of equally likely outcomes.

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