Licence plates

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Licence plates

by avenus » Sun May 31, 2009 10:35 am
A license plate in the country Kerrania consists of four digits followed by two letters. The letters A, B, and C are used only by government vehicles while the letters D through Z are used by non-government vehicles. Kerrania's intelligence agency has recently captured a message from the country Gonzalia indicating that an electronic transmitter has been installed in a Kerrania government vehicle with a license plate starting with 79. If it takes the police 10 minutes to inspect each vehicle, what is the probability that the police will find the transmitter within three hours?

A) 18/79
B) 1/6
C) 1/25
D) 1/50
E) 1/900
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Re: Licence plates

by dtweah » Sun May 31, 2009 4:45 pm
avenus wrote:A license plate in the country Kerrania consists of four digits followed by two letters. The letters A, B, and C are used only by government vehicles while the letters D through Z are used by non-government vehicles. Kerrania's intelligence agency has recently captured a message from the country Gonzalia indicating that an electronic transmitter has been installed in a Kerrania government vehicle with a license plate starting with 79. If it takes the police 10 minutes to inspect each vehicle, what is the probability that the police will find the transmitter within three hours?

A) 18/79
B) 1/6
C) 1/25
D) 1/50
E) 1/900
7 9 --- --- ---- ----

The number of government vehicles having plates beginning with 79 is
1 x 1 x 10 x 10 x 3 x 3=900

900 x 10min =9000mins is needed to search all these vehicles.
3hrs is 180 mins.

Prob = 180/9000=1/50

Choose D.

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by avenus » Tue Jun 02, 2009 1:06 am
OA is D