Statistics and Probability (IMO Mathematics Olympiad Class 9): Questions 77  82 of 101
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Question number: 77
» Statistics and Probability
Question
A box contains 8 balls out of which x are black. If one ball is drawn at random from the box, what is the probability that it will be a black ball? If 4 more black balls are put in the box, the probability of drawing a black ball is now double of what is was before, then x is________
Choices
Choice (4)  Response  

a.  3 

b.  2 

c.  9 

d.  6 

Question number: 78
» Statistics and Probability
Question
Two dice are thrown simultaneously, the odds in favour of getting the sum 5 is________
Choices
Choice (4)  Response  

a. 


b. 


c. 


d. 


Question number: 79
» Statistics and Probability
Question
The median of the observation 2, 1, 12, 29, 25, 12, 10, 4, 5 is ________
Choices
Choice (4)  Response  

a.  12 

b.  25 

c.  15 

d.  10 

Question number: 80
» Statistics and Probability
Question
The mean of 24 observations is 35. If the mean of the first 12 observations is 31 and that of the last 12 observations is 38, then the 12^{th} observation is ________
Choices
Choice (4)  Response  

a.  14 

b.  15 

c.  11 

d.  12 

Question number: 81
» Statistics and Probability
Question
In a mathematics test given to 15 students, the following marks (out of 100) is recorded: 45, 56, 78, 54, 75, 34, 68, 98, 87, 99, 90, 76, 55, 77, 68, then mean, median and mode of this data are respectively ________
Choices
Choice (4)  Response  

a.  60.67, 75, 65 

b.  70.67, 77, 68 

c.  70.67, 75, 68 

d.  55.26, 78, 65 

Question number: 82
» Statistics and Probability
Question
Average of 10 numbers is 12. What should be added as 11^{th} number to make the average 13?
Choices
Choice (4)  Response  

a.  28 

b.  25 

c.  30 

d.  23 
