164
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:   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.

Subject: Average
Q:

The standard deviation of the set {10, 10, 10, 10, 10} is

A) 0 B) 1
C) 5 D) 10
 
Answer & Explanation Answer: A) 0

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2 483
Q:

If the average of 31, x, 42, 39, 56, 78, 83 and 91 is 58.5, then what is the value of x?

 

A) 26 B) 34
C) 58 D) 48
 
Answer & Explanation Answer: D) 48

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2 3892
Q:

The mode and median of the data 8, 6, 8, 7, 8, 6, 8, 7, 6 is

A) 7 and 8 B) 6 and 7
C) 8 and 7 D) 6 and 8
 
Answer & Explanation Answer: C) 8 and 7

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1 576
Q:

The mean of the data 1, 2, 10, 18, 3, 17, 19 is

A) 7 B) 10
C) 17 D) 70
 
Answer & Explanation Answer: B) 10

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1 413
Q:

If the average age of 20 students in Class-I is 10 years and average age of 25 students in Class II is 12 years, find the average age (in years) of all students.

A) 11 B) 11.111
C) 10.50 D) 10.85
 
Answer & Explanation Answer: B) 11.111

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0 651
Q:

20 pens and 46 pencils were purchased for Rs. 235. If the average price of a pencil is Rs. 2.50 then calculate the average price (in Rs.) of a pen.

A) 6 B) 4
C) 8 D) 12
 
Answer & Explanation Answer: A) 6

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2 530
Q:

The average of two numbers is 10 and the product of two numbers is 96. Find the two numbers.

 

 

A) 3, 32 B) 12, 8  
C) 1, 96   D) 24, 4
 
Answer & Explanation Answer: B) 12, 8  

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Q:

Average of the runs of 133 players of a team is 38. If the average of the runs of the male players is 43 and the average of the runs of the female players is 24, then what will be the ratio of the total runs of male players and the total runs of female players respectively?

 

A) 301 : 60   B) 7 : 3  
C) 39 : 11   D) 60 : 207
 
Answer & Explanation Answer: A) 301 : 60  

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