Statistics and Probability (IMO Mathematics Olympiad Class 9): Questions 23  28 of 101
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Question number: 23
» Statistics and Probability
Question
The mean of ten items is x and if each item is increased by 4, then its mean will be ________
Choices
Choice (4)  Response  

a. 


b. 


c. 


d. 


Question number: 24
» Statistics and Probability
Question
Cards marked with the numbers 2 to 101 are placed in a box and mixed thoroughly. One card is drawn from this bag. The probability that the number on the card is a prime less than 20 is ________
Choices
Choice (4)  Response  

a. 


b. 


c. 


d. 


Question number: 25
» Statistics and Probability
Question
If the mean of 20 observations is 25 and that of another 5 observations is 14, then the mean of 25 observations is ________
Choices
Choice (4)  Response  

a.  22.8 

b.  22 

c.  15 

d.  15.5 

Question number: 26
» Statistics and Probability
Question
In a class test, in English, 25 students scored 70 marks, 40 students scored 65 marks and 35 scored 50 marks. The mean of their score is (approximately) ________
Choices
Choice (4)  Response  

a.  65 marks 

b.  29 marks 

c.  45 marks 

d.  61 marks 

Question number: 27
» Statistics and Probability
Question
The average of 20 numbers is calculated as 30. It is discovered later on that while calculating the average one number, namely 40 was wrongly read as 20. The correct average is________
Choices
Choice (4)  Response  

a.  26 

b.  31 

c.  28 

d.  25 

Question number: 28
» Statistics and Probability
Question
The mean weight of 120 students in a class is 100 kg. The mean weight of boys is 110 kg while that of the girls is 90 kg. The number of boys and girls are________
Choices
Choice (4)  Response  

a.  60, 60 

b.  40, 30 

c.  70, 40 

d.  10, 50 
