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:

Amithab's average expenditure for the January to June is Rs. 4200 and he spends Rs.1200 in January and Rs.1500 in july.The average expenditure for the months of febraury to July is:

A) Rs. 4250 B) Rs. 4520
C) Rs. 4060 D) None of these
 
Answer & Explanation Answer: A) Rs. 4250

Explanation:

Amithab's total expenditure for Jan - June  = 4200 x 6 = 25200

 

Expenditure for Feb - June = 25200-1200 = 24000

 

Expenditure for the months of Feb - July = 24000 + 1500 =25500

 

The average expenditure = 25500/6 = 4250

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9 11036
Q:

Five boxes of bananas sell for Rs. 30. how many boxes can you buy for Rs.9?

A) 2 B) 1.5
C) 1.25 D) 2.5
 
Answer & Explanation Answer: B) 1.5

Explanation:

Given Five boxes of bananas sell for Rs. 30.

=> 1 Box of Bananas for = 30/5 = Rs. 6

 

Then, for Rs. 9

=> 9/6 = 3/2 = 1.5

 

Hence, for Rs. 9, 1.5 box of bananas can buy.

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25 10951
Q:

The average monthly salary of the employees of a firm is Rs.60 out of the employees 12 officers get an average of Rs.400 per month and the rest an average of Rs. 56 per month , Find the number of emp

Answer

Actual average salary of 12 officers = 400


\inline \fn_jvn \therefore Total salary of 12 officers = 400 x 12 = 4800


Average of these 12  officers as a whole =60


Total salary of 12 officers as a whole = 60 x 12 = 720


The total salary of rest  = 4800 - 720 = 4080


Difference in average of the rest of officers  = 60 - 56 = 4


Rest of the officers = \inline \fn_jvn \frac{4080}{4}=1020


Total number of employees = 1020 + 12 = 1032

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51 10921
Q:

The average of 9 results is 50. The average of first four results is 52 and average of last four results is 49 . what is the fifth result?

Answer

Total of results = 50 x 9 = 450


Total of first four results = 52 x 4 = 208


Total of Last four results = 49 x 4 = 196


Hence the fifth result = 450 - (208 + 196) = 46

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22 10900
Q:

Find the average of first 20 multiples of 9.

 

A) 94.8 B) 94.7
C) 94.6 D) 94.5
 
Answer & Explanation Answer: D) 94.5

Explanation:
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Q:

The average of 26,29,n,35 and 43 lies between 25 and 35. If n is always an integer and greater than the average  of the given integers then the value of n is :

A) 33 B) 34
C) 33 D) None of these
 
Answer & Explanation Answer: C) 33
Explanation:

Average of 26,29,35 and 43 is 33.25 . Also the average of 26 , 29, n, 35 and 43 lies between 25 and 35 i.e,

 25<26+29+n+35+435<35 

=> 125 < 26+29+n+35+43 < 175 

=> 125 < 133 + n < 175

=> n < 42

 Since the value of n is an integer and greater than 33.25 then 33 < n < 42 for every integer n.

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9 10679
Q:

The average of the two-digit numbers, which remain the same when the dibits inter-change their positions, is :

A) 53 B) 54
C) 55 D) 56
 
Answer & Explanation Answer: C) 55

Explanation:

Average = (11 + 22 + 33 + 44 + 55 + 66 + 77 + 88 + 99) / 9

             =( (11 + 99) + (22 + 88) + (33 + 77) + (44 + 66) + 55) / 9

             = (4 * 110 + 55)/9 =  495 / 9 = 55. 

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10 10580
Q:

The average weight of 45 passengers in a bus is 52 kg. 5 of them whose average weight is 48 kg leave the bus and other 5 passengers whose average weight is 54 kg join the bus at the same stop. What is the new average weight of the bus?   

A) 54.21 kgs B) 51.07 kgs
C) 52.66 kgs D) 53.45 kgs
 
Answer & Explanation Answer: C) 52.66 kgs

Explanation:

Given total number of passengers in the bus = 45

First average weight of 45 passengers = 52 kgs

Average weight of 5 passengers who leave bus = 48

Average weight of passengers who joined the bus = 54

Therefore, the net average weight of the bus is given by

= 45 x 52 - 5 x 48 + 5 x 5445 = 237045= 1583= 52.66 kgs.

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31 10219