167
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:

Out of 6 numbers, the sum of the first 5 numbers is 7 times the 6th number. If their average is 136, then the 6th number is:

 A) 116 B) 102 C) 96 D) 84

Explanation:

0 15
Q:

Ina class of 40 students, 45% are girls and the remaining are boys. If the average of the girls’ marks is 54 and that of the boys is 46, what is the average of the whole class?

 A) 49.6 B) 49.7 C) 49.8 D) 49.5

Explanation:

0 61
Q:

In a class of 60 students, 40% are girls. The average weight of the whole class is 59.2 kg and the average weight of the girls is 55 kg. What is the average weight of the boys?

 A) 62 kg B) 61 kg C) 60 kg D) 63 kg

Explanation:

1 118
Q:

In a class of 60 students, 40% are girls. The average weight of the boys is 62kg and that of the girls is 55kg. What is the average weight of the whole class?

 A) 59.2kg B) 58.6kg C) 58.8kg D) 59kg

Explanation:

2 138
Q:

In a class of 40 students, 60% are girls. The average of the girls’ marks is 72 and that of the boys is 54. What are the average marks of the whole class?

 A) 65 B) 64.8 C) 65.4 D) 65.2

Explanation:

1 134
Q:

The average of five consecutive even numbers is M.If the next five even numbers are also included, the average of ten numbers will be:

 A) M + 5 B) 11 C) 10 D) M + 10

Explanation:

1 218
Q:

The average of the first four numbers is three times the fifth number. If the average of all the five numbers is 85.8, then the fifth number is:

 A) 33 B) 34 C) 39 D) 29

Explanation:

2 285
Q:

The average of the first four numbers is three times the fifth number. If the average of all the five numbers is 85.8, then the fifth number is:

 A) 33 B) 34 C) 39 D) 29

Explanation:

Let the fifth number be x.
The average of the first four numbers = 3x
Sum of all the first four numbers = 3x = 12x
The average of all the five numbers = 85.8
Sum of all the five numbers = 85.8 5 = 429
Sum of all the first four numbers + 5th number = 429
12x + x = 429
x = 429/13 = 33
The 5th number is 33.