Microsoft Interview Question
Senior Software Development EngineersCountry: India
Interview Type: In-Person
Shouldn't it be
(1-Y)^4 = 0.1
?
(1-Y)^4
is the probability that the bus would NOT pass for 20 mins.
0.9 is the probability that the bus WOULD pass in 20 mins.
Let,
p(5) : probability of seeing no bus in 5 mins.
P(10): p(5)*p(5) = p(5)^2
similarly, p(20) = p(5)^4
also,
1-p(20) = probability of seeing bus in 20 mins
1-p(20) = 0.9 ....(given in question)
p(20)= 0.1
but, p(20) = p(5)^4
hence p(5) = p(20)^1/4
p(5) = 0.1^1/4 = 0.5623
p(seeing a bus in 5 mins) = 1- p(seeing no car in 5 mins)
p(seeing a bus in 5 mins) = 1-0.5623
p(seeing a bus in 5 mins) = 0.4377
Therefore probability of seeing a bus is 0.4377
Let the probabilty of passing of bus in the time intersection of 5 min be X.
- aasshishh April 27, 2013Then the probabilty of not passing of bus in the same 5 minute intersection is Y=1-X.
Let the bus not pass for 4 '5 min intersection', i.e, for 20 mins.
The probablity of above will be Y^4.
Then as per question,
1 - Y^4 = 0.9
Y^4 = 0.1
(1-X)^4 = 0.1
X = 0.4377