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 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 (arithmetic mean) amount of savings of ten students is Rs. 600. Three of the students have no savings at all and each of the others have at least Rs. 250 including Nihar, who has exactly Rs. 1300. The largest amount, in Rs., that any one student could have is

A) 3250 B) 3450
C) 3650 D) 3850
 
Answer & Explanation Answer: B) 3450

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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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Q:

The average weight of 10 parcels is 1.7 kg. Addition of another new parcel reduces the average weight by 60 gram. What is the weight , in kg, of the new parcel?

A) 1.04 B) 1.08
C) 1.4 D) 1.8
 
Answer & Explanation Answer: A) 1.04

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Q:

A batsman has a certain average of runs for 12 innings. In the 13th inning he scores 96 runs thereby increasing his average by 5 runs. What will be his average after 13th inning?

A) 28 B) 32
C) 36 D) 42
 
Answer & Explanation Answer: C) 36

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Q:

A group of boys has an average weight of 36 kg. One boy weighing 42 kg leaves the group and another boy weighing 30 kg joins the group. If the average now becomes 35.7 kg, then how many boys are there in the group?

A) 30 B) 32
C) 40 D) 56
 
Answer & Explanation Answer: C) 40

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Q:

The average of 9 observations was found to be 35. Later on, it was detected that an observation 81 was misread as 18. The correct average of the observations is

A) 28 B) 42
C) 35 D) 45
 
Answer & Explanation Answer: B) 42

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Q:

The mean of 100 observations was calculated as 40. It was found later on that one of the observations was misread as 83 instead of 53. The correct mean is:

A) 39 B) 39.7
C) 40.3 D) 42.7
 
Answer & Explanation Answer: B) 39.7

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