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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-10 section-3

Each section contains 100 MCQs on Average .
91
The average age of 10 children is 9 years 9 months. The average of 9 children is 8 years 11 months. What is the age of the tenth child ?
Discuss
Answer & Solution
Answer: Option A
Solution:
Average age of 10 children = 9 years 9 months
Sum of ages of 10 children = 9 × 10 + $$\frac{9}{12}$$ × 10 = $$\frac{390}{4}$$
Average age of 9 children = 8 years 11 months
Sum of age of 9 children = 8 × 9 + $$\frac{11}{12}$$ × 9 = $$\frac{321}{4}$$
Age of 10th child
= $$\frac{390}{4}$$ - $$\frac{321}{4}$$
= $$\frac{69}{4}$$
= 17 years 3 months
92
The average weight of 20 students in a class is increased by 0.75 kg when one student of 35 kg replaced by a new student. Weight of the new student (in kg) is :
Discuss
Answer & Solution
Answer: Option D
Solution:
Let the weight of the new student = x kg
According to the question,
$$\frac{x - 35}{20}$$ = 0.75
⇒ x - 35 = 15
⇒ x = 50
93
In a pre school, the average weight of 30 girls in a class among 50 students is 16 kg and that of the remaining students is 15.5 kg. What is the average weight of all the students in the class ?
Discuss
Answer & Solution
Answer: Option B
Solution:
According to the question,
Average = $$\frac{30 × 16 + 20 × 15.5}{50}$$
= $$\frac{480 + 310}{50}$$
= $$\frac{790}{50}$$
= 15.8 kg
94
Out of nine persons, 8 persons spent Rs. 30 each for their meals. The ninth one spent Rs. 20 more than the average expenditure of all the nine. The total money spent by all of them was :
Discuss
Answer & Solution
Answer: Option C
Solution:
Let the average of 9 people expenditure = Rs. x
According to the question,
⇒ $$\frac{30 × 8 + x + 20}{9}$$    = x
⇒ 240 + 20 + x = 9x
⇒ 260 = 8x
⇒ x = $$\frac{260}{8}$$
⇒ x = 32.5
Total expenditure are
= 32.5 × 9
= Rs. 292.50
95
A man had 7 children. When their average age was 12 years, a child aged 6 years died. Then average age of remaining six children is :
Discuss
Answer & Solution
Answer: Option A
Solution:
According to the question,
Average age of 7 children = 12 years
Sum of ages of 7 children = 84 years
If a child aged 6 years died then
Sum of aged of 6 children = 84 - 6 = 78 years
∴ Average = $$\frac{78}{6}$$ = 13 years
96
In a class, the average score of girls in an examination is 73 and that of boys is 71. The average score for the whole class is 71.8. Find the percentage of girls :
Discuss
Answer & Solution
Answer: Option A
Solution:
Let the number of girls = x
And, the number of boys = y
According to the question,
73x + 71y = 71.8 (x + y)
1.2x = 0.8y
$$\frac{x}{y}$$ = $$\frac{2}{3}$$
∴ Girls% = $$\frac{2}{2 + 3}$$ × 100
= $$\frac{2}{5}$$ × 100
= 40%
97
If the average of 6 consecutive even number is 25, the difference between the largest and the smallest number is :
Discuss
Answer & Solution
Answer: Option B
Solution:
According to the question,
Sum of 6 consecutive even number is = 25 × 6 = 150
Sn = $$\frac{n}{2}$$ [2a +(n - 1) × d]
⇒ 150 = $$\frac{6}{2}$$ [2a + (6 - 1) × 2]
⇒ 150 = $$\frac{6}{2}$$ (2a + 10)
⇒ 300 = 12a + 60
⇒ 12 a = 240
⇒ a = $$\frac{240}{12}$$
⇒ a = 20
∴ Numbers are 20, 22, 24, 26, 28, 30
Difference between largest and smallest is
= 30 - 20
= 10

Alternate :
Let the 6 consecutive number is
= x, x + 2, x + 4, x + 6, x + 8, x + 10
According to the question,
Largest number = Average + (n - 1) = 25 + 5 = 30
Smallest number = Average - (n - 1) = 25 - 5 = 20
Difference between largest and smallest number
= 30 - 20
= 10
98
The sum of three consecutive even numbers is 28 more than the average of these three number. Then the smallest of these number is -
Discuss
Answer & Solution
Answer: Option C
Solution:
Let consecutive even number x, x + 2, x + 4
According to the question,
(x + x + 2 + x + 4) - $$\frac{(x + x + 2 + x +4)}{3}$$
$$\frac{3(3x + 6) - (3x + 6)}{3}$$    = 28
2 (3x + 6) = 28 × 3
3x + 6 = 42
3x = 36
x = 12
So, smallest number = x = 12
99
A man purchased 7 bags of rice at the rate of Rs. 800 each, 8 bags of rice at Rs. 1000 each and 5 bags of rice at the rate of Rs. 1200 each. What is the average cost of one bag of rice ?
Discuss
Answer & Solution
Answer: Option B
Solution:
According to the question,
Average
= $$\frac{7 × 800 + 8 × 1000 + 5 × 1200}{20}$$
= $$\frac{5600 + 8000 + 6000}{20}$$
= $$\frac{19600}{20}$$
∴ Average = Rs. 980
100
The average of 30 numbers is 40 and that of other 40 numbers is 30. The average of all the numbers is :
Discuss
Answer & Solution
Answer: Option A
Solution:
According to the question,
Average of 30 numbers is = 40
Sum of 30 numbers is = 40 × 30 = 1200
Average of 40 numbers is = 30
Sum of 40 numbers is = 40 × 30 = 1200
Total average = $$\frac{1200 + 1200}{70}$$
= $$\frac{2400}{70}$$
= $$34\frac{2}{7}$$