GATE | Gate IT 2007 | Question 55
In a multi-user operating system on an average, 20 requests are made to use a particular resource per hour. The arrival of requests follows a Poisson distribution. The probability that either one, three or five requests are made in 45 minutes is given by :
(A) 6.9 × 106 × e-20
(B) 1.02 × 106 × e-20
(C) 6.9 × 103 × e-20
(D) 1.02 × 103 × e-20
Answer: (B)
Explanation: In 1 hr. requests received =20
So in 45 min requests received = 15
So, lemda = 15
So, using poission distribution formula: P(x; μ) = (e-μ) (μx) / x!
p(one request) + p(3 request) + p(5 request)
= p(1; 15) + p(3; 15) + p(5; 15)
= 6.9 * 103 * e-15
= 1.02 × 106 × e-20
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