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Q:

If x is chosen at random from the set {1,2,3,4} and y is to be chosen at random from the set {5,6,7}, what is the probability that xy will be even?

A) 1/2	B) 2/3
C) 3/4	D) 4/3

Answer & Explanation Answer: B) 2/3

Explanation:

S ={(1,5),(1,6),(1,7),(2,5),(2,6),(2,7),(3,5),(3,6),(3,7),(4,5),(4,6),(4,7)}
Total element n(S)=12

xy will be even when even x or y or both will be even.
Events of x, y being even is E.
E ={(1,6),(2,5),(2,6),(2,7),(3,6),(4,5),(4,6),(4,7)}
n(E) = 8

P(E)=n(E)n(S)=812 = 4/3

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Filed Under: Probability

Q:

There are four hotels in a town. If 3 men check into the hotels in a day then what is the probability that each checks into a different hotel?

A) 1/2	B) 3/4
C) 4/7	D) 3/8

Answer & Explanation Answer: D) 3/8

Explanation:

Total cases of checking in the hotels = 4 x 4 x 4 = 64 ways.

Cases when 3 men are checking in different hotels = 4×3×2 = 24 ways.

Required probability =24/64 = 3/8

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Filed Under: Probability

Q:

What is the cause of thrashing? How does the system detect thrashing? Once it detects thrashing, what can the system do to eliminate this problem?

Answer

Thrashing is caused by under allocation of the minimum number of pages required by a process, forcing it to continuously page fault. The system can detect thrashing by evaluating the level of CPU utilization as compared to the level of multiprogramming. It can be eliminated by reducing the level of multiprogramming.

What_is_the_cause_of_thrashing_How_does_the_system_detect_thrashing_Once_it_detects_thrashing,_what_can_the_system_do_to_eliminate_this_problem1557490890.jpg image

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Subject: Operating Systems

Q:

A bag contains 12 white and 18 black balls. Two balls are drawn in succession without replacement. What is the probability that first is white and second is black?

A) 6/145	B) 36/145
C) 18/95	D) 12/145

Answer & Explanation Answer: B) 36/145

Explanation:

The probability that first ball is white:
=C112C130=1230=25

Since, the ball is not replaced; hence the number of balls left in bag is 29.
Hence the probability the second ball is black:
=C118C129=1829

Required probability =(25)×(1829)

=36/145

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Filed Under: Quantitative Aptitude - Arithmetic Ability

Q:

Four dice are thrown simultaneously. Find the probability that all of them show the same face.

A) 1/216	B) 1/36
C) 2/216	D) 4/216

Answer & Explanation Answer: A) 1/216

Explanation:

The total number of elementary events associated to the random experiments of throwing four dice simultaneously is:

= $6 * 6 * 6 * 6 = 6^{4}$

n(S) = $6^{4}$

Let X be the event that all dice show the same face.

X = { (1,1,1,1,), (2,2,2,2), (3,3,3,3), (4,4,4,4), (5,5,5,5), (6,6,6,6)}

n(X) = 6

Hence required probability = $\frac{n (X)}{n (S)} = \frac{6}{6^{4}}$ = $\frac{1}{216}$

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Filed Under: Probability

Q:

What resources are used when a thread is created? How do they differ from those when a process is created?

Answer

When a thread is created the threads does not require any new resources to execute the thread shares the resources like memory of the process to which they belong to. The benefit of code sharing is that it allows an application to have several different threads of activity all within the same address space. Whereas if a new process creation is very heavyweight because it always requires new address space to be created and even if they share the memory then the inter process communication is expensive when compared to the communication between the threads.

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Subject: Operating Systems

Q:

A number X is chosen at random from the numbers -3, -2, -1, 0, 1, 2, 3. What is the probability that |X|<2

A) 3/7	B) 3/4
C) 4/5	D) 5/7

Answer & Explanation Answer: A) 3/7

Explanation:

X can take 7 values.
To get |X|+2) take X={−1,0,1}

=> P(|X|<2) = Favourable CasesTotal Cases = 3/7

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Filed Under: Probability

Q:

A man sells Rs.5000, 12 % stock at 156 and uinvests the proceeds parity in 8 % stock at 90 and 9 % stock at 108. He hereby increases his income by Rs. 70. How much of the proceeds were invested in each stock?

A) 4000	B) 4200
C) 4002	D) 4020

Answer & Explanation Answer: B) 4200

Explanation:

S.P of Rs. 5000 stock = $R s . (\frac{156}{100} * 5000)$ = Rs. 7800.

Income from this stock = $R s . (\frac{12}{100} * 5000)$ = Rs. 600.

Let investment in 8 % stock be x and that in 9 % stock = (7800 - x).

Therefore,

$(x * \frac{8}{90}) + (7800 - x) * \frac{9}{108} = [600 + 70]$

$\frac{4 x}{45} + \frac{7800 - x}{12} = 670 \Leftrightarrow x = 3600$

Therefore, Money invested in 8 % stock at 90 = Rs. 3600.

Money invested in 9 % at 108 = Rs. (7800-3600) = Rs. 4200.

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Filed Under: Stocks and Shares

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