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:

The mean of 10 observations is 17. One more observation is included and the new mean becomes 16. The 11th observation is

 

A) 16 B) 8
C) 6 D) 12
 
Answer & Explanation Answer: C) 6

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Q:

Of the 3 numbers whose average is 40, the first is 1/3 rd the sum of other 2. What is the first number?

A) 20 B) 50
C) 25 D) 30
 
Answer & Explanation Answer: D) 30

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Q:

There are a total of 200 students in a school, of which 7/10th are boys. Find the number of girls in the school.

A) 80 B) 60
C) 40 D) 120
 
Answer & Explanation Answer: B) 60

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Q:

The mean of marks secured by 60 students in division A of class X is 66, 45 students of division B is 62 and that of 75 students of division C is 60. Find the mean of marks of the students of three divisions of Class X.

A) 61.8 B) 62.5
C) 61.1 D) 63.9
 
Answer & Explanation Answer: B) 62.5

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Q:

The mean of marks secured by 30 students in division-A of class X is 67, 55 students of division-B is 63 and that of 40 students of division-C is 61. What is the mean of marks of the students of three divisions of Class X?

A) 63.32 B) 62.62
C) 61.92 D) 64.72
 
Answer & Explanation Answer: A) 63.32

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Q:

The mean of the 5 smallest numbers from a group is 15 while the mean of all the 13 members of the group taken together is 17. What is the mean of the 8 largest numbers?

A) 18.50 B) 17.75
C) 18.75 D) 18.25
 
Answer & Explanation Answer: D) 18.25

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Q:

The mean score in a test of the 12 boys in a class was 16 while the overall mean of the 30 students in the class was 18.1. What was the mean score of the girls?

A) 19.8 B) 20.5
C) 20 D) 19.5
 
Answer & Explanation Answer: D) 19.5

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Q:

In a class of 50 students there are 27 girls. The average weight of these girls is 45 kg and average weight of the full class is 49.6 kgs. What is the average weight of the boys of the class?

A) 55 B) 54.2
C) 53.4 D) 53
 
Answer & Explanation Answer: A) 55

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