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 Average Questions

Popular Latest Rated Important Formulae

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 weight of a class of 24 students is 35 kg. If the weight of the teacher be included, the average rises by 400 g. The weight of the teacher is : 

A) 45 kg B) 46 kg
C) 47 kg D) 48 kg
 
Answer & Explanation Answer: A) 45 kg

Explanation:

Weight of the teacher = (35.4 x 25 - 35 x 24) kg = 45 kg.

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229 64013
Q:

The mean of 50 observations was 36. It was found later that an observation 48 was wrongly taken as 23. The corrected new mean is :

A) 35 B) 36.5
C) 40 D) 42
 
Answer & Explanation Answer: B) 36.5

Explanation:

Correct Sum = (36 * 50 + 48 - 23) = 1825.

Correct mean = = 1825/50 = 36.5

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182 56102
Q:

The average of 11 numbers is 10.9. If the average of the first six numbers is 10.5 and that of the last six numbers is 11.4, then the middle number is :

A) 10.5 B) 11.5
C) 12.5 D) 13.5
 
Answer & Explanation Answer: B) 11.5

Explanation:

Middle numbers  =  [(10.5 x 6 + 11.4 x 6) - 10.9 x 11] = (131.4 - 119-9) = 11.5.

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100 52417
Q:

A library has an average of 510 visitors on Sundays and 240 on other days. The average number of visitors per day in a month of 30 days beginning with a Sunday is : 

A) 285 B) 290
C) 297 D) 305
 
Answer & Explanation Answer: A) 285

Explanation:

 Since the month begins with a Sunday, so there will be five Sundays in the month,

Required average = (510 * 5 + 240 * 25) / 30 = 8550/30 = 285.

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74 48510
Q:

The average temperature for Monday, Tuesday, Wednesday and Thursday was 48 degrees and for Tuesday, Wednesday, Thursday and Friday was 46 degrees. If the temperature on Monday was 42 degrees. Find the temperature on Friday ?

A) 34 B) 36
C) 38 D) 40
 
Answer & Explanation Answer: A) 34

Explanation:

M + Tu + W + Th = 4 x 48 = 192
Tu + W + Th + F = 4 x 46 = 184
M = 42
Tu + W + Th = 192 - 42 = 150
F = 184 – 150 = 34

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62 43068
Q:

10 years ago, the average age of a family of 4 members was 24 years. Two children having been born (with age diference of 2 years), the present average age of the family is the same. The present age of the youngest child is :

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

Explanation:

Total age of 4 members, 10 years ago = (24 x 4) years = 96 years.

 

Total age of 4 members now = [96 + (10 x 4)] years = 136 years.

 

Total age of 6 members now = (24 x 6) years = 144 years.

 

Sum of the ages of 2 children = (144 - 136) years = 8 years.

 

Let the age of the younger child be x years.

 

Then, age of the elder child = (x+2) years.

 

So, x+(x+2) =8 <=> x=3

 

Age of younger child  =  3 years.

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131 40843
Q:

After replacing an old member by a new member, it was found that the average age of five members of a club is the same as it was 3 years ago. What is the difference between the ages of the replaced and the new member ?

A) 12 B) 13
C) 14 D) 15
 
Answer & Explanation Answer: D) 15

Explanation:

i) Let the ages of the five members at present be a, b, c, d & e years. 

And the age of the new member be f years. 

ii) So the new average of five members' age = (a + b + c + d + f)/5 ------- (1) 

iii) Their corresponding ages 3 years ago = (a-3), (b-3), (c-3), (d-3) & (e-3) years 

So their average age 3 years ago = (a + b + c + d + e - 15)/5 = x ----- (2) 

==> a + b + c + d + e = 5x + 15 

==> a + b + c + d = 5x + 15 - e ------ (3) 

iv) Substituting this value of a + b + c + d = 5x + 15 - e in (1) above, 

The new average is: (5x + 15 - e + f)/5 

Equating this to the average age of x years, 3 yrs, ago as in (2) above, 

(5x + 15 - e + f)/5 = x 

==> (5x + 15 - e + f) = 5x 

Solving e - f = 15 years. 

Thus the difference of ages between replaced and new member = 15 years.

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164 39595
Q:

A car owner buys petrol at Rs 7.50, Rs. 8 and Rs. 8.50 per litre for three successive years. What approximately is the average cost per litre of petrol if he spends Rs. 4000 each year ?

A) 6.23 B) 7.98
C) 8.97 D) 9.89
 
Answer & Explanation Answer: B) 7.98

Explanation:

Total quantity of petrol consumed in 3 years =(4000/7.50+4000/8+4000/8.50)  liters

 

                                                         = 4000(2/15+1/8+2/17) liters                                                   

 

                                                         = 76700/51 liters

 

Total amount spent = Rs. (3 x 4000) = Rs. 12000.

 

Average cost = Rs. (12000*51/76700) = Rs. 7.98.

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