166
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

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.

Q:

24 students collected money for donation. The average contribution was ₹50. Later on, their teacher also contributed some money. Now the average contribution is ₹56. The teacher’s contribution is:

 A) ₹56 B) ₹200 C) ₹106 D) ₹194

Explanation:

7 9391
Q:

Average of 8 numbers is 40. The average of first three numbers is 46 and the average of next two numbers is 50. If the sixth number is 6 and 10 less than seventh and eighth number respectively, then what is the value of eighth number?

 A) 28 B) 22 C) 30 D) 32

Explanation:

6 1095
Q:

1800 chocolates were distributed among the students of a class. Each student got twice as many chocolates as the number of students in the class. Calculate the number of students in the class.

 A) 30 B) 40 C) 60 D) 90

Explanation:

4 837
Q:

The average of 60 student’s results is 38. If the average of the first 22 students is 36, and that of the last 32 students is 32, then the average result of the remaining students is:

 A) 81 B) 77 C) 65 D) 52

Explanation:

7 985
Q:

The average score in Mathematics of 90 students of sections A and B together is 49. The number of students in A was 25% more than that of B, and the average score of the students in B was 20% higher than that of the students in A. What is the average score of the students in A?

 A) 44.5 B) 45 C) 44 D) 45.5

Explanation:

4 860
Q:

Out of the five subjects, the average marks of Suman in first 3 Subjects was 81 and the average marks in the last 3 subjects was 74. If her marks in the third subject was 65, then what was her average marks in all the subjects?

 A) 75 B) 76 C) 79 D) 80

Explanation:

0 798
Q:

The average of 26 numbers is 37. One more number is added and the new average becomes 41. What is that new number?

 A) 140 B) 145 C) 146 D) 147

Explanation:

3 799
Q:

The median of the first 25 whole numbers is:

 A) 10 B) 12.5 C) 15 D) 12