GMAT Practice Question: If a certain coin is flipped, the probability that the coin will land heads up is 1/2...
Question
If a certain coin is flipped, the probability that the coin will land heads up is 1/2. If the coin is flipped 5 times, what is the probability that it will land heads up on the first 3 flips and not on the last 2 flips?
- 3/5
- 1/2
- 1/5
- 1/8
- 1/32
Topics: probability
Solution
Step 1
We first translate "the probability that the coin will land heads up is 1/2", giving the probability of heads and tails.
P(H) = 1/2 P(T) = 1 - 1/2 = 1/2
Step 2
We then multiply the probabilities of independent flips to find the probability that the coin lands heads on the first three flips and tails on the last two flips.
P(H then H then H then T then T) = P(H)^3 P(T)^2 = (1/2)^3 (1/2)^2 = (1/2)^5 = 1/32
Answer
1/32
