At 3 pm, Jennifer went into labor. There is a 70% chance her baby will : Problem Solving (PS)

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At 3 pm, Jennifer went into labor. There is a 70% chance her baby will

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Math Expert

Joined: 02 Sep 2009

Posts: 51223

At 3 pm, Jennifer went into labor. There is a 70% chance her baby will [#permalink]

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29 Jan 2018, 04:41

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Difficulty:

45% (medium)

Question Stats:

63% (01:36) correct

38% (01:14) wrong

based on 70 sessions

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At 3 pm, Jennifer went into labor. There is a 70% chance her baby will be born each hour that she is in labor. What is the probability that her baby will be born at 6 pm on the same day?

(A) 0.027
(B) 0.063
(C) 0.147
(D) 0.27
(E) 0.343

Spoiler: OA

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Re: At 3 pm, Jennifer went into labor. There is a 70% chance her baby will [#permalink]

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29 Jan 2018, 05:17

Bunuel wrote:

If the probability that the baby is born in an hour is 0.7(70%),
then the probability that the baby is not born in that hour is 0.3

If the baby is to born at 6, the baby can't be born at 4 or 5,
but must definitely be born at 6.
The probability that the baby is born at 6 is $0.3*0.3*0.7 =$ 0.063(Option B)
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Re: At 3 pm, Jennifer went into labor. There is a 70% chance her baby will [#permalink]

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29 Jan 2018, 06:24

P(Born)= 0.7; P(not born)= 0.3
for the baby to be born at 6 pm, we have
P(not born 4 pm) * P(not born 5 pm) * P(born 6 pm) = 0.3*0.3*0.7 = 0.063
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Re: At 3 pm, Jennifer went into labor. There is a 70% chance her baby will [#permalink]

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30 Jan 2018, 10:18

Bunuel wrote:

For the baby to be born at 6 pm, the baby can not be born at 4 pm nor at 5 pm. Note that since the probability that the baby is born at each hour is 0.7, the probability that the baby is not born in that hour is 1 - 0.7 = 0.3. Thus, the probability that the baby is born at 6pm is (0.3) x (0.3) x (0.7) = 0.063.

Answer: B
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