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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-2 section-3

Each section contains 100 MCQs on Average .
11
The average of 50 numbers is 38. If the numbers 45 and 55 are discarded, then the average of the remaining numbers is-
Discuss
Answer & Solution
Answer: Option C
Solution:
Sum of 50 numbers = 38 × 50 = 1900
Sum of remaining 48 numbers
= 1900 - (45 + 55)
= 1800
∴ Required average
= $$\left( {\frac{{1800}}{48}} \right)$$
= 37.5
12
Out of three numbers, the first is twice the second and is half of the third. If the average of the three numbers is 56, then difference of first and third numbers is
Discuss
Answer & Solution
Answer: Option D
Solution:
Let the second number be x
Then, first number = 2x, 3rd number = 4x
∴ 2x + x + 4x = 56 × 3
⇒ 7x = 168
⇒ x = 24
∴ Required difference
= 4x - 2x
= 2x
= 2 × 24
= 48
13
The average price of three items of furniture is Rs. 15000. If their prices are in the ratio 3 : 5 : 7, the price of the cheapest item is-
Discuss
Answer & Solution
Answer: Option A
Solution:
Let their prices be 3x, 5x and 7x respectively
Then,
⇒ 3x + 5x + 7x = 15000 × 3
⇒ 15x = 45000
⇒ x = 3000
∴ Cost of cheapest item
= Rs. (3000 × 3)
= Rs. 9000
14
A school has 4 sections of chemistry in Class X having 40, 35, 45 and 42 students. The mean marks obtained in Chemistry test are 50, 60, 55 and 45 respectively for the 4 sections. Determine the overall average of marks per student.
Discuss
Answer & Solution
Answer: Option C
Solution:
Average marks
$$\eqalign{ & = \left( {\frac{{50 \times 40 + 60 \times 35 + 55 \times 45 + 45 \times 42}}{{40 + 35 + 45 + 42}}} \right) \cr & = \left( {\frac{{2000 + 2100 + 2475 + 1890}}{{162}}} \right) \cr & = \left( {\frac{{8465}}{{162}}} \right) \cr & = 52.25 \cr} $$
15
The mean of 5 observations is 60, the mean of 10 observations is 30 and the mean of 15 observations is 20. The mean of all the 30 observations is-
Discuss
Answer & Solution
Answer: Option C
Solution:
Required mean
$$\eqalign{ & = \left( {\frac{{60 \times 5 + 30 \times 10 + 20 \times 15}}{{5 + 10 + 15}}} \right) \cr & = \left( {\frac{{300 + 300 + 300}}{{30}}} \right) \cr & = \left( {\frac{{900}}{{30}}} \right) \cr & = 30 \cr} $$
16
In a class there are 32 boys and 28 girls. The average age of the boys in the class is 14 years and the average age of the girls in the class 13 years. What is the average age of the whole class (rounded to two digits after decimal) ?
Discuss
Answer & Solution
Answer: Option D
Solution:
Required average
$$\eqalign{ & = \left( {\frac{{32 \times 14 + 28 \times 13}}{{32 + 28}}} \right) \cr & = \left( {\frac{{448 + 364}}{{60}}} \right) \cr & = \left( {\frac{{812}}{{60}}} \right) \cr & = 13.53 \cr} $$
17
The average annual income (in Rs.) of certain agricultural workers is S and that of other workers is T. The number of agricultural workers is 11 times that of other workers. Then the average monthly income (in Rs.) of all the workers is-
Discuss
Answer & Solution
Answer: Option D
Solution:
Let the number of other workers be x
Then, number of agricultural workers = 11x
Total number of workers = 12x
∴ Average monthly income
$$\eqalign{ & = \frac{{S \times 11x + T \times x}}{{12x}} \cr & = \frac{{11S + T}}{{12}} \cr} $$
18
The average mark of student in 4 subjects is 75. If the student obtained 80 marks in the fifth subject, then the new average is-
Discuss
Answer & Solution
Answer: Option B
Solution:
Sum of marks in 4 subjects
= 75 × 4
= 300
Sum of marks in 5 subjects
= 300 + 80
= 380
∴ New average
= $$\frac{380}{5}$$
= 76
19
The average of 7 consecutive numbers is 20. The largest of these numbers is-
Discuss
Answer & Solution
Answer: Option C
Solution:
Let the number be x, x + 1, x + 2, x + 4, x + 5 and x + 6
Then,
$$ \Rightarrow \frac{{x + \left( {x + 1} \right) + \left( {x + 2} \right) + \left( {x + 3} \right) + \left( {x + 4} \right) + \left( {x + 5} \right) + \left( {x + 6} \right)}}{7} = 20$$
$$\eqalign{ & \Rightarrow 7x + 21 = 140 \cr & \Rightarrow 7x = 119 \cr & \Rightarrow x = 17 \cr} $$

∴ Largest number
= x + 6 = 17 + 6
= 23
20
Of four numbers whose average is 60, the first is one-fourth of the sum of the last three. The first number is -
Discuss
Answer & Solution
Answer: Option D
Solution:
Let the four numbers be a, b, c and d respectively
Then,
⇒ a = $$\frac{1}{4}$$ (b + c + d)
⇒ b + c + d = 4a
Also,
a + b + c + d = 60 × 4 = 240
⇒ a + 4a = 240
⇒ 5a = 240
⇒ a = 48
Hence, first number = 48