66
Q:

# A speaks truth in 75% of cases and B in 80% of cases. In what percentage of cases are they likely to contradict each other, narrating the same incident

 A) 30/100 B) 35/100 C) 45/100 D) 50/100

Explanation:

Let   A = Event that A speaks the truth

B = Event that B speaks the truth

Then P(A) = 75/100 = 3/4

P(B) = 80/100 = 4/5

P(A-lie) = $1-34$= 1/4

P(B-lie) = $1-45$= 1/5

Now, A and B contradict each other =[A lies and B true] or [B true and B lies]

= P(A).P(B-lie) + P(A-lie).P(B)

= $35*15+14*45=720$

= $720*100$= 35%

Q:

X attempts 100 questions and gets 340 marks. If for every correct answer is 4 marks and wrong answer is negative one mark, then the number of questions wrongly answered by Mr. X is:

 A) 14 B) 15 C) 12 D) 13

Explanation:

6 706
Q:

If the standard deviation of 0, 1, 2, 3 ......... 9 is K, then the standard deviation of 10, 11, 12, 13 ........... 19 will be:

 A) K+1 B) K C) K+4 D) K+8

Explanation:

2 1196
Q:

The standard deviation of the set {10, 11, 12, 9, 8} is

 A) 1 B) √2 C) 2 D) 2√2

Explanation:

8 926
Q:

Find the range of the data 2, 1, 2, 3, 5, 4, 7, 3, 5, 2, 4.

 A) 5 B) 4 C) 3 D) 6

Explanation:

1 1172
Q:

Find the median, mode and mean of 9, 5, 8, 9, 9, 7, 8, 9, 8.

 A) 9, 9, 9 B) 9, 8, 9 C) 8, 9, 8 D) 8, 9, 9

Explanation:

3 903
Q:

In the usual set notation,  =

 A) A∪B∪A∪C B) A∩B∪A∩C C) A∪B∩A∪C D) A∪B∩A∩C

Explanation:

1 3315
Q:

Find the range and mode of the data 17, 18, 28, 19, 16, 18, 17, 29, 18

 A) 12 and 18 B) 13 and 18 C) 12 and 17 D) 11 and 17

Explanation:

1 1144
Q:

Find the standard deviation of {11, 7, 10,13, 9}

 A) 1 B) 2 C) 4 D) 5