No heads at all — Probability Aptitude Question
No heads at all: Four fair coins are tossed. What is the probability of getting no heads? Answer and worked solution on CodeKairo.
- Topic: Probability
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 40 seconds
Question
Four fair coins are tossed. What is the probability of getting no heads?
Options
- 1/16
- 1/8
- 1/4
- 1/2
Show the answer and the worked solution
Correct answer: A. 1/16
Worked solution
- All four must be tails: (1/2)⁴ = 1/16.
Answer: 1/16.
The idea
Independent events multiply. The complement, 'at least one head', is 15/16.
Shortcut. No heads is the single outcome TTTT; halving once per coin gives 1/2 → 1/4 → 1/8 → 1/16.
Common trap. "1/8" — stopping one halving short, which is the answer for three coins; four coins need (1/2)⁴ = 1/16.