FACTS  AND  FORMULAE  FOR  AVERAGE QUESTIONS

 

 

1. Average =Sum of observationsNo. of observations

2. Suppose a man covers a certain distance x kmph and an equal distance at y kmph. Then, the average speed during the whole journey is2xyx+yKmph

Q:

What is the average of all numbers between 9 and 90 which are divisible by 8?

A) 53 B) 52
C) 51 D) 50
 
Answer & Explanation Answer: B) 52

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Q:

The average height of 30 boys out of a class of 50 is 160 cm. If the average height of the remaining boys is 165 cm, the average height of the whole class (in cm) is:

A) 161 B) 162
C) 163 D) 164
 
Answer & Explanation Answer: B) 162

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Q:

The average marks in science subject of a class of 20 students is 68. If the marks of two students were misread as 48 and 65 of the actual marks 72 and 61 respectively, then what would be the correct average?

A) 68.5 B) 69
C) 69.5 D) 70
 
Answer & Explanation Answer: B) 69

Explanation:

Difference of marks = 72 + 61 –48 –65 = 20∴Correct average marks = 68 +20/20= 69

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Q:

The mean of marks secured by 50 students in division A of class X is 61, 25 students of division B is 57 and that of 50 students of division C is 55. What will be the mean of marks of the students of three divisions of Class X?

A) 57.1 B) 56.4
C) 59.2 D) 57.8
 
Answer & Explanation Answer: D) 57.8

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Q:

In the first 40 overs of a 50 over innings, the run rate was 4.8 runs/over. What is the required run rate in the remaining 10 overs to reach the target of 241 runs?

A) 6.7 B) 6.5
C) 6.3 D) 4.9
 
Answer & Explanation Answer: D) 4.9

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Q:

A librarian purchased 60 story books for his library. But he found that he could get 4 extra books by spending Rs 336 more and then the overall average price per book would be reduced by Re 1. The previous average price of each book was

A) Rs 84 B) Rs 83
C) Rs 68 D) Rs 100
 
Answer & Explanation Answer: D) Rs 100

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Q:

What is the average of all numbers between 100 and 200 which are divisible by 13?

A) 147.5 B) 145.5
C) 143.5 D) 149.5
 
Answer & Explanation Answer: D) 149.5

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Q:

The average marks obtained by a group of 16 students was 20. One student left the group as a result of which the average of the remaining students rose to 21. But another student joined, as a result of which the average marks of the group dropped a bit and became 20.5. What was the average marks obtained by the student who left and the one who joined?

A) 10 B) 11
C) 8 D) 9
 
Answer & Explanation Answer: D) 9

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