Average Question & Answers
The average of 20 numbers is zero. Of them, at the most, how many may be greater than zero ?
A) 0B) -1C) 1D) none of these
Answer & ExplanationAnswer: A) 0
Explanation:
Average of 20 numbers = 0.
It is quite possible that 19 of these numbers may be positive and if their sum is a, then 20th number is (- a).
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Subject: Average - Quantitative Aptitude - Arithmetic Ability
A grocer has a sale of Rs 6435, Rs. 6927, Rs. 6855, Rs. 7230 and Rs. 6562 for 5 consecutive months. How much sale must he have in the sixth month so that he gets an average sale of Rs, 6500 ?
A) 4991B) 5467C) 5987D) 6453
Answer & ExplanationAnswer: A) 4991
Explanation:
Total sale for 5 months = Rs. (6435 + 6927 + 6855 + 7230 + 6562) = Rs. 34009.
= Rs. (39000 - 34009)
= Rs. 4991.
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Subject: Average - Quantitative Aptitude - Arithmetic Ability
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) 12B) 13C) 14D) 15
Answer & ExplanationAnswer: 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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Subject: Average - Quantitative Aptitude - Arithmetic Ability
A pupil's marks were wrongly entered as 83 instead of 63. Due to that the average marks for the class got increased by half. The number of pupils in the class is :
A) 45B) 40C) 39D) 37
Answer & ExplanationAnswer: B) 40
Explanation:
Let there be x pupils in the class.
Total increase in marks = (x * 1/2) = x/2.
x/2 = (83 - 63) => x/2 = 20 => x = 40.
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Subject: Average - Quantitative Aptitude - Arithmetic Ability
The average of five consecutive odd numbers is 61. What is the difference between the highest and lowest numbers :
A) 4B) 8C) 12D) 16
Answer & ExplanationAnswer: B) 8
Explanation:
Let the numbers be x, x + 2, x + 4, x + 6 and x + 8.
Then [x + (x + 2) + (x + 4) + (x + 6) + (x + 8) ] / 5 = 61.
or 5x + 20 = 305 or x = 57.
So, required difference = (57 + 8) - 57 = 8
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