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A study found that 80% of drivers, who ride with a passenger, wear sea

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A study found that 80% of drivers, who ride with a passenger, wear sea [#permalink]

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New post 30 Jan 2018, 07:05
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Difficulty:

  15% (low)

Question Stats:

84% (01:50) correct 16% (01:12) wrong based on 43 sessions

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A study found that 80% of drivers, who ride with a passenger, wear seatbelts. Passengers wear seatbelts 70% of the time when the driver wears a seatbelt, and 55% of the time when the driver doesn't wear a seatbelt. What is the probability that a passenger wears a seatbelt?

A. 11%
B. 33%
C. 56%
D. 67%
E. 80%
[Reveal] Spoiler: OA

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Re: A study found that 80% of drivers, who ride with a passenger, wear sea [#permalink]

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New post 30 Jan 2018, 07:21
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D

lets say there are 100 drivers and 100 passengers.

80 driver wear seatbelts and 20 dont.

70% passengers wear seatbelt when the driver wears seatbelt. i.e 80*0.7=56 passengers wear seatbelt

55% passengers wear seatbelt when the driver doesn''t wear seatbelt. i.e 20*0.55=11 passengers wear seatbelt

so on a total 56+11 =67 passengers wear seatbelt. Hence 67%
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Re: A study found that 80% of drivers, who ride with a passenger, wear sea [#permalink]

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New post 31 Jan 2018, 00:08
Bunuel wrote:
A study found that 80% of drivers, who ride with a passenger, wear seatbelts. Passengers wear seatbelts 70% of the time when the driver wears a seatbelt, and 55% of the time when the driver doesn't wear a seatbelt. What is the probability that a passenger wears a seatbelt?

A. 11%
B. 33%
C. 56%
D. 67%
E. 80%


Solution



Image

Thus, the correct answer is Option D.

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Re: A study found that 80% of drivers, who ride with a passenger, wear sea [#permalink]

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New post 08 Feb 2018, 01:35
Bunuel wrote:
A study found that 80% of drivers, who ride with a passenger, wear seatbelts. Passengers wear seatbelts 70% of the time when the driver wears a seatbelt, and 55% of the time when the driver doesn't wear a seatbelt. What is the probability that a passenger wears a seatbelt?

A. 11%
B. 33%
C. 56%
D. 67%
E. 80%


Total probability = 0.8(When the Driver wears seat belt)*0.7(When the Passenger wears seat belt) + 0.2(When the Driver doesn't wear seat belt)*0.7(When the Passenger wears seat belt) = 0.67
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Re: A study found that 80% of drivers, who ride with a passenger, wear sea   [#permalink] 08 Feb 2018, 01:35
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A study found that 80% of drivers, who ride with a passenger, wear sea

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