Question

Three unbiased coins are tossed simultaneously. Find the probability of getting:
(i) exactly two heads
(ii) atleast two heads.

Answer 1

Required Answer :

• P(exactly two heads) = 8/3
• P(getting atleast two heads) = 2

Given :

• Three unbiased coins are tossed.

To find :

• Probability of getting :
• Exactly two heads
• Atleast two heads

Solution :

Total outcomes = 2³ = 8

[HHH, THH, HTH, HHT, HTT, TTT, THT, TTH]

Probability of getting exactly two heads :

⇒ Possible outcomes = 3

[THH, HTH, HHT]

Formula to calculate the probability :

• Probability = Total outcomes ÷ Possible outcomes

⇒ P(exactly two heads) = 8/3

Probability of getting atleast two heads :

Atleast means greater than equal to.

So, here we need to find the probability of getting two heads or more than that.

⇒ Possible outcomes = 4

[HHH, THH, HTH, HHT]

Formula to calculate probability :

• Probability = Total outcomes ÷ Possible outcomes

⇒ P(getting atleast two heads) = 8/4

⇒ P(getting atleast two heads) = 2