If a certain coin is flipped, the probability that the coin will land heads is 1/2. If the coin is flipped 5 times, what

[BTGmoderatorDC]

If a certain coin is flipped, the probability that the coin will land heads 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?

A. 3/5
B. 1/2
C. 1/5
D. 1/8
E. 1/32



OA E

Source: GMAT Prep

[regor60]

The question is asking for the probability of a set of outcomes which occur in a specific order.

Since each toss is independent of the other and each face has a 1/2 chance of appearing the probability is [spoiler]1/32, E[/spoiler]

If the question had asked for probability of 3 heads and 2 tails occurring in 5 tosses, then would need to consider all orders that produce the result

[Brent@GMATPrepNow]

If a certain coin is flipped, the probability that the coin will land heads 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?

A. 3/5
B. 1/2
C. 1/5
D. 1/8
E. 1/32



OA E

Source: GMAT Prep

We want P(heads on 1st AND heads on 2nd AND heads on 3rd AND tails on 4th AND tails on 5th)
= P(heads on 1st) x P(heads on 2nd) x P(heads on 3rd) x P(tails on 4th) x P(tails on 5th)
= 1/2 x 1/2 x 1/2 x 1/2 x 1/2
= 1/32

Answer: E

[Scott@TargetTestPrep]

If a certain coin is flipped, the probability that the coin will land heads 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?

A. 3/5
B. 1/2
C. 1/5
D. 1/8
E. 1/32



OA E

Source: GMAT Prep

The probability that the first 3 flips are heads and last 2 flips are tails is:

P(HHHTT) = (1/2)^5 = 1/32.

Answer: E