This set of Aptitude Questions and Answers (MCQs) focuses on “Addition and Subtraction”.

1. The average age of 5 boys of a class is 15. If 7 more boys are admitted to the class with average age 12, and 3 of the existent boys leave the class with the average age 13, what will be the new average age of the boys of the class?

a) 6.1

b) 6.2

c) 6.3

d) 6.4

View Answer

Explanation: Total age of the existent boys = 5 * 15 = 75

Total age of the newly admitted boys = 7 * 12 = 84

Total age of the boys who left the class = 13 * 3 = 39

Total age of the class newly formed = 75 + 84 – 39 = 120

Total number of boys in new class = 15 + 7 – 3 = 19

Average of the newly formed class = 120 / 19 = 6.3

2. The average monthly pay of 40 employees is 25000. Out of which 11 employees who were paid 20000 were removed. 22 employees were newly hired with annual pay of 144000. Find the new average quarterly salary of the employees to the nearest rupee.

a) 20,862

b) 20,863

c) 30,862

d) 30,863

View Answer

Explanation: Total salary of the past 40 employees = 40 * 25000 = 10,00,000

Total salary of the employees removed = 11 * 20000 = 2,20,000

Total salary of the newly hired employees = 1,44,000 * 22 = 31,68,000 per annum

31,68,000 / 12 = 2,64,000 per month.

New total payable salary per month = 10,00,000 + 2,64,000 – 2,00,000 = 10,64,000

Total number of new employees = 40 – 11 = 22 = 51

Average salary = 10,64,000 / 51 = 20,862.74 = 20,863

3. The average of 10 numbers is 50. If 2 new numbers are added, the total is increased by 100. 4 existing numbers are taken out, the total is decreased by 50%. Find the average of the new numbers.

a) 32

b) 35.5

c) 37.5

d) 28

View Answer

Explanation: Total of the initial numbers = 10 * 50 = 500

Total of new numbers added = 100

New total = 500 + 100 = 600

Total decreased after 4 numbers taken out = 50% = 50 * 600 / 100 = 300

New average = 300 / 8 = 37.5

4. Find the average of 10 numbers formed after 10 taken out from the average of first 22 prime numbers.

a) 22.5

b) 32.5

c) 42.5

d) 47.5

View Answer

Explanation: First 22 prime numbers: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73 and 79.

Sum of first 22 prime numbers = 715

Average of first 22 prime numbers = 715 / 22 = 32.5

32.5 – 10 = 22.5

5. 11 is subtracted from the average of first 11 prime numbers. Then the average of the first 9 even numbers is added to it. Find the average resulting group of numbers.

a) 3.54

b) 13.54

c) 4.54

d) 14.54

View Answer

Explanation: Average of first 11 prime numbers = (2 + 3 + 5 + 7 + 11 + 13 + 17 + 19 + 23 + 29 + 31) / 11

= 160 / 11 = 14.54

11 subtracted from the average = 14.54 – 11 = 3.54

Average of first 9 even numbers = (2 + 4 + 6 + 8 + 10 + 12 + 14 + 16 + 18) / 9 = 10

Sum of the new group = 3.54 + 10 = 13.54

5. There are 5 members in a family. One of them died due to some disease. If the average age of the family is decreased by 20% of what it was before, find the age of the deceased person if the average before was 50 years.

a) 60

b) 70

c) 80

d) 90

View Answer

Explanation: The total age before the member died = 50 * 5 = 250

The new average = 20% less than the old average = 50 – 20% of 50 = 50 – 10 = 40

New average = 40

Total number of family members now = 4

New total = 40 * 4 = 160

Age of the deceased person = old – new total = 250 – 160 = 90 years.

6. 10 people applied for a job with average experience of 5 years. The company demanded for a minimum of 4 years of experience. Due to this norm 4 candidates were set out. The average experience of candidates now is 7 years. Find the average experience of the candidates set out.

a) 1 year

b) 1.5 years

c) 2 years

d) 2.5 years

View Answer

Explanation: Total experience at the beginning = 10 * 5 = 50 years

Total of the remaining candidates = 7 * 6 = 42 years

Total of candidates set out = 50 – 42 = 8 years

Average of the candidates set out = 8 / 4 = 2 years.

7. What is the value when average of first 20 even numbers is added to the sum of first 5 two – digit palindrome numbers and first 10 odd numbers.

a) 74

b) 68

c) 54

d) 48

View Answer

Explanation: Average of first 20 even numbers = 420 / 20 = 21

Average of first 5 two – digit palindrome numbers = (11 + 22 + 33 + 44 + 55) / 5 = 33

Average of first 20 odd numbers = 400 / 20 = 20

The value = 21 + 33 + 20 = 74

8. 20 people work for a company for a monthly package of 20 thousand each. 5 of them got an increment of 10 %, 10 of them got an increment of 50 % rest of them were set off by the company. Find the average of the new salaries of the employees.

a) 25000

b) 26666.66

c) 27111.11

d) 27333.33

View Answer

Explanation: Increment of the first 5 = 10% of 20000 = 2000

Increment of the next 10 employees = 50% of 20000 = 10000

New total expenditure of the company = 2000 * 5 + 10000 * 10 + 20000 * 15

= 10000 + 100000 + 300000 = 410000

Total number of active employees = 20 – 5 = 15

Average of current salaries = 410000 / 15 = 27333.33

9. A total of 5000 is taken out from the average of 50 values, the new average is 20. Find the initial average.

a) 15.66

b) 16.33

c) 16.66

d) 17.33

View Answer

Explanation: Let the initial average be x.

The initial sum = 50 * x = 50x

The final average = 50x – 5000 = 20x

50x – 20x = 5000

30x = 5000

X = 5000 / 30 = 16.6

10. Raj was dictating some numbers to his friend Raju. He misread 43 as 34 and 65 as 56. Find the difference caused in the average if there were a total of 12 digits and the average with wrong digits is 23.

a) 1

b) 1.5

c) 2

d) 2.5

View Answer

Explanation: Wrong sum = 12 * 23 = 276

Right sum = 276 + 9 + 9 = 294

Wrong average = 23

Right average = 294 / 12 = 24.5

Difference between the averages = 24.5 – 23 = 1.5

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