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Quantitative Aptitude

AVERAGES MCQs

Averages

Total Questions : 3752 | Page 9 of 376 pages
Question 81.

Of the four numbers, the first is twice the second, the second is one-third of the third and the third is 5 times the fourth. The average of the numbers is 24.75. The largest of these numbers is:

  1.    9
  2.    15
  3.    30
  4.    45
  5.    None of these
 Discuss Question
Answer: Option D. -> 45
 -  Let the fourth number be a
Then, third number = 5a, second number = 5a 3 And first number = 10a 3 x + 5x + 5x 3 + 10x 3 = (24.75 x 4) or 11x = 99 or x = 9.                 So, the numbers are 9, 45, 15 and 30
Largest number = 45
Question 82.

The average of six numbers is 3.95. The average of two of them is 3.4, while the average of the other two is 3.85. What is the average of the remaining two numbers?

  1.    4
  2.    4.6
  3.    5
  4.    5.6
  5.    None of these
 Discuss Question
Answer: Option B. -> 4.6
 -  Sum of the remaining two numbers = (3.95 x 6) – [(3.4 x 2) + (3.85 x 2)]
                                                         
                                                         = 23.70 - (6.8 + 7.7) = 23.70 - 14.5 = 9.20
Average = 9.2/2 = 4.6
Question 83.

The average age of students of a class is 15.8 years. The average age of boys in the class is 16.4 years and that of the girls is 15.4 years. The ratio of the number of boys to the number of girls in the class is:

  1.    1 : 2
  2.    2 : 3
  3.    3 : 4
  4.    4 : 5
  5.    None of these
 Discuss Question
Answer: Option B. -> 2 : 3
 -  Let the ratio be k:1
Then, k x 16.4 + 1 x 15.4 = (k + 1) x 15.8
(16.4 - 15.8) k = (15.8 - 15.4)
k = 0.4 = 2 0.6 3
Required Ratio =2 : 3
Question 84.

The average age of the boys in a class is 16 years and that of the girls is 15 years. The average age for the whole class is:

  1.    15
  2.    16
  3.    17
  4.    Data inadequate
  5.    None of these
 Discuss Question
Answer: Option D. -> Data inadequate
 -  Clearly, to find the average, we ought to know the number of boys, girls or students in the class, neither of which has been given
So, the data provided is inadequate
Question 85.

The average price of 10 books is Rs. 12 while the average price of 8 of these books is Rs. 11.75. Of the remaining two books, if the price of one book is 60% more than the price of the other, what is the price of each of these two books?

  1.    Rs 10 and Rs 16
  2.    Rs 10 and Rs 24
  3.    Rs 24 and Rs 16
  4.    Rs 24 and Rs 12
  5.    None of these
 Discuss Question
Answer: Option A. -> Rs 10 and Rs 16
 -  Total price of the two books = Rs. [(12 x 10) – (11.75 x 8)]
                                                = Rs. (120 - 94) = Rs. 26
Let the price of one book be Rs.x
Then, the price of other book = Rs. (x + 60% of x) = x + 3 5 x   = Rs.   8x 5  
 
So, x + 8x 5 = 26    
Question 86.

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?

  1.    7.98
  2.    8.58
  3.    8.32
  4.    4.98
  5.    None of these
 Discuss Question
Answer: Option A. -> 7.98
 -   Quantity of petrol consumed in 3 years =   4000 7.50 + 4000 8 + 4000 8.50   litres       = 4000 ( 2 15 + 1 8 + 2 17 ) =   76700 51   litres       Total amount spent = Rs. (3 x 4000) = Rs. 12000.       Average cost =.   12000 x 51 76700   = Rs. 6120 767 = Rs. 7.98
Question 87.  what is the average of the following numbers ? 5720175, 5819038, 4847211, 9815742, 7242158, 8432766
  1.    6979515
  2.    6721575
  3.    708445
  4.    6835185
 Discuss Question
Answer: Option A. -> 6979515
Explanation :
Question 88.  find the average of the following set of scores. 124, 856, 331, 227, 963, 338, 259, and 662
  1.    230
  2.    380
  3.    470
  4.    520
 Discuss Question
Answer: Option C. -> 470
Explanation :
Question 89.  the mean marks of 30 students in a class is 58.5. later on, it was found that 75 was wrongly recorded as 57. find the correct mean.
  1.    57.1
  2.    58.1
  3.    59.1
  4.    80.1
 Discuss Question
Answer: Option C. -> 59.1
Explanation :
Question 90.  in a class, there are 20 boys whose average age is decreased by 2 months, when one boy aged 18 years is replaced by a new boy.find the age of new boy.
  1.    11 years 10 months
  2.    12 years 2 months
  3.    13 years 6 months
  4.    14 years 8 months
 Discuss Question
Answer: Option D. -> 14 years 8 months
Explanation :

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