Question

A coin is tossed 4 times. What is the probability of getting heads exactly 3 times?

• A. 1/4
• B. 3/8
• C. 1/2
• D. 3/4

Answer 1

The correct option is A 1/4

We use binomial distribution
Let x: number of heads
Here n=4
Required probability is P(x=3)
$={}^4{C}_3{\left(\frac{1}{2}\right)}^3{\left(\frac{1}{2}\right)}^1=\frac{1}{4}$

Alternative Solution:

Favourable outcomes = {HHHT, HHTH, HTHH, THHH} = 4

Total number of outcomes$=2^4=16$

Required probability$=\frac{4}{16}=\frac{1}{4}$