747
Q:

A bag contains 6 white and 4 black balls .2 balls are drawn at random. Find the probability that they are of same colour.

A) 1/2 B) 7/15
C) 8/15 D) 1/9

Answer:   B) 7/15



Explanation:

Let S be the sample space

 

Then n(S) = no of ways of drawing 2 balls out of (6+4) =10C2 10 =10*92*1 =45

 

Let E = event of getting both balls of same colour

 

Then,n(E) = no of ways (2 balls out of six) or (2 balls out of 4)

 

                =6C2+4C2 = 6*52*1+4*32*1= 15+6 = 21

 

Therefore, P(E) = n(E)/n(S) = 21/45 = 7/15

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
 
Answer & Explanation Answer: C) 12

Explanation:
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5 675
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
 
Answer & Explanation Answer: B) K

Explanation:
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2 1113
Q:

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

A) 1 B) √2
C) 2 D) 2√2
 
Answer & Explanation Answer: B) √2

Explanation:
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8 908
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
 
Answer & Explanation Answer: D) 6

Explanation:
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1 1098
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
 
Answer & Explanation Answer: C) 8, 9, 8

Explanation:
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3 841
Q:

In the usual set notation, A  (B  C) =

 

 

A) A∪B∪A∪C B) A∩B∪A∩C
C) A∪B∩A∪C D) A∪B∩A∩C
 
Answer & Explanation Answer: C) A∪B∩A∪C

Explanation:
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1 3236
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
 
Answer & Explanation Answer: B) 13 and 18

Explanation:
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1 1075
Q:

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

A) 1 B) 2
C) 4 D) 5
 
Answer & Explanation Answer: B) 2

Explanation:
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2 1030