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 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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Q:

Given below are the ages in yrs of a group of children. What is the medium age?

 

7, 9, 8, 6 , 5, 3, 9, 2



A) 6.5 B) 5
C) 6.125 D) 6
 
Answer & Explanation Answer: A) 6.5

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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Q:

The median of the data 1, 1/2, 1/2, 3/4, 1/4, 2, 1/2, 1/4, 3/4 is

 

A) 1/4 B) 1/2
C) 1/6 D) 3/4
 
Answer & Explanation Answer: B) 1/2

Explanation:
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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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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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Q:

A cicketer bas a certain average for 10 innings, In the eleventh inning, he scorod 108 runs, thereby increasing his average by 6 runs. His new average is :

A) 44 runs B) 46 runs
C) 48 runs D) 49 runs
 
Answer & Explanation Answer: C) 48 runs

Explanation:

Let average for 10 innings be x. Then,

(10x + 108)/11 = x + 6 => 11x + 66 = 10x + 108  =>  x = 42.

New average = (x + 6) = 48 runs.

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Q:

The average expenditure of the hotel when there are 10 guests is Rs. 60 per guests and the average expenditure is Rs.40 when there are 20 Guests. If it is known that there are some fixed expenses irrespective of the number of guests then the average expenditure per guest  whe there are 40 guests in the hotel.

A) Rs. 30 B) Rs. 25
C) Rs. 20 D) can't be determined
 
Answer & Explanation Answer: A) Rs. 30

Explanation:

Let the fixed expenditure of the hotel be Rs.x and the variable expenditure ( which is dependent on the guest ) is Rs.y , then 

          x + 10y = 600        ---------(1)

          x + 20y = 800       ----------(2)

From (1) & (2)

10y = 200 

=>  y = Rs. 20   and    x= 400

 

Hence the total expenditure when there are 40 guests = 400 + 40 x 20 = 1200

 

Therefore,  average expenditure = 1200/40 = Rs. 30

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