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Average - Aptitude MCQ Questions and Solutions with Explanations

Average MCQ Questions and answers with easy and logical explanations.Arithmetic Ability provides you all type of quantitative and competitive aptitude mcq questions on Average with easy and logical explanations. Average MCQ is important for exams like Banking exams,IBPS,SCC,CAT,XAT,MAT etc. Page-1 section-5

Each section contains 100 MCQs on Average .
1
The average of 9 observations was found to be 35. Later on, it was detected that an observation 81 was misread as 18. The correct average of the observation is -
Discuss
Answer & Solution
Answer: Option B
Solution:
Difference = 81 - 18 = 63
So, change in average = $$\frac{+ 63}{9}$$ = + 7
Correct average = 35 + 7 = 42
2
Out of 20 boys, 6 are each of 1 m 15 cm height, 8 are of 1 m 10 cm and rest of 1 m 12 cm. The average height of all of them is :
Discuss
Answer & Solution
Answer: Option A
Solution:
According to the question,
Height of 6 persons
= 6 × 1 m 15 cm = 6 m 90 cm
Height of 8 persons
= 8 × 1 m 10 cm = 8 m 80 cm
Height of 6 persons
= 6 × 1 m 12 cm = 6 m 72 cm
Total Height of 20 persons
= 22 m 42 cm
Average = $$\frac{{22{\text{ m }}42{\text{ cm}}}}{{20}}$$   = 1 m 12.1 cm
3
The average of the largest and smallest 3 digits numbers formed by 0, 2 and 4 would be :
Discuss
Answer & Solution
Answer: Option A
Solution:
According to the question,
Largest number = 420
Smallest number = 204
Average
= $$\frac{420 + 204}{2}$$
= $$\frac{624}{2}$$
= 312
4
The average of five numbers is 7. If three new numbers would be added, then the new average comes out to be 8.5. What is the average of those three new numbers ?
Discuss
Answer & Solution
Answer: Option C
Solution:
Sum of 5 numbers = 7 × 5 = 35
Sum of 8 numbers = 8.5 × 8 = 68
Sum of added all three numbers = 68 - 35 = 33
Average of three new numbers = $$\frac{33}{3}$$ = 11
5
The average age of a family with 5 members is 28. If one of the 5 members of age 20 is excluded the average age of the family becomes -
Discuss
Answer & Solution
Answer: Option C
Solution:
Total age of 5 members = 5 × 28 = 140
And, required average
= $$\frac{140 - 20}{4}$$
= $$\frac{120}{4}$$
= 30 years
6
The average of 6 observations is 45.5. If one new observation is added to the previous observations, then the new average becomes 47. The new observation is :
Discuss
Answer & Solution
Answer: Option B
Solution:
Let the new observation be = x
According to the question,
6 × 45.5 + x = 7 × 47
273.0 + x = 329
x = 329 - 273
x = 56
7
The average pocket money of 3 friend A, B, C is Rs. 80 in a particular month. If B spends double and C spends triple of what A spends during that month and if the average of their unspent pocket money is Rs. 60, then A spends (in Rs.)-
Discuss
Answer & Solution
Answer: Option A
Solution:
According to the question,
Pocket money
$$\eqalign{ & \Rightarrow \frac{{A + B + C}}{3} = 80 \cr & \Rightarrow A + B + C = 240 \cr} $$
Unspent pocket money
$$\eqalign{ & \Rightarrow \frac{{A + B + C}}{3} = 60 \cr & \Rightarrow A + B + C = 180 \cr} $$
Spent pocket money = 240 - 180 = Rs. 60
Given:
$$\frac{B}{A} = \frac{2}{1}\,\,{\text{and}}\,\,\frac{C}{A} = \frac{3}{1}$$
    A     B     C   
Spent   1 2 3  = 6 units
6 units -------- 60
1 unit --------- 10
∴ A spent = 1 × 10 = Rs. 10
8
The average age of group of 20 girls is 15 years and that of another group of 25 boys it is 24 years. The average age of the two groups mixed together is :
Discuss
Answer & Solution
Answer: Option B
Solution:
According to the question,
The average age of 20 girls is = 15 years
The average age of 25 boys is = 24 years
∴ Mixed average
= $$\frac{20 × 15 + 25 × 24}{45}$$
= $$\frac{300 + 600}{45}$$
= $$\frac{900}{45}$$
= 20 years
9
The average of nine number is 50. The average of first five numbers is 54 and that of the last three numbers is 52. Then the sixth number is :
Discuss
Answer & Solution
Answer: Option C
Solution:
Average of 9 numbers = 50
Hence sum of 9 numbers = 450
Average of last three numbers = 52
Hence sum of them will be = 156
Average of first five numbers is = 54
Hence sum of them will be = 54 × 5 = 270
So 6th number will be = sum of 9 numbers - (sum of first five numbers + sum of last three numbers)
= 450 - (156 + 270)
= 24
10
From a class of 42 boys, a boy aged 10 years goes away and in his place, a new boy is admitted. If on account of this change, the average age of the boys in that class increases by 2 months, the age of the newcomer is :
Discuss
Answer & Solution
Answer: Option B
Solution:
According to the question,
Due to newcomer average age is increased by = 2 months
Total age increment in 42 boys
= 42 × 2
= 84 months or 7 years
Note : If the age of newcomer is same as the boy which was replaced then there is no effect on 2 months.
∴ Age of new boy
= 10 + 7
= 17 years