About this quiz
50 questions covering every section of the note.
This Lok Sewa practice set has 50 multiple-choice questions (Subject: Maths and IQ · For: Kharidar, Nayab Subba, Section Officer · Level: Easy). Take the quiz above first; after that, use the study list below to revise every question with its correct answer and a short explanation.
Study list: all 50 questions with answers and explanations
What is the average of 4, 8, 12, 16 and 20?
- A) 10
- B) 12 ✔
- C) 14
- D) 16
Why: Sum = 60, number = 5, so the average is 60 ÷ 5 = 12.
The average of the first 20 natural numbers is:
- A) 10
- B) 10.5 ✔
- C) 11
- D) 20
Why: Average of first n natural numbers = (n + 1) ÷ 2 = 21 ÷ 2 = 10.5.
The average of the first 10 even numbers is:
- A) 10
- B) 10.5
- C) 11 ✔
- D) 12
Why: Average of first n even numbers = n + 1 = 11. (2 + 4 + ... + 20 = 110; 110 ÷ 10 = 11)
The average of the first 15 odd numbers is:
- A) 15 ✔
- B) 16
- C) 14
- D) 30
Why: Average of first n odd numbers = n = 15.
The average of 8 numbers is 15. Their sum is:
- A) 23
- B) 100
- C) 120 ✔
- D) 150
Why: Sum = Average × Number = 15 × 8 = 120.
The average of 10 numbers is 30. If 5 is added to each number, the new average is:
- A) 30
- B) 35 ✔
- C) 50
- D) 80
Why: Adding 5 to every number adds 5 to the average: 30 + 5 = 35.
The average of 6 numbers is 12. If each number is multiplied by 4, the new average is:
- A) 16
- B) 24
- C) 48 ✔
- D) 72
Why: Multiplying every number by 4 multiplies the average by 4: 12 × 4 = 48.
The average age of 25 students is 12 years. When the teacher's age is included, the average becomes 13 years. The teacher's age is:
- A) 25 years
- B) 38 years ✔
- C) 13 years
- D) 40 years
Why: 26 × 13 = 338 and 25 × 12 = 300, so the teacher is 338 − 300 = 38 years.
The average weight of 10 men increases by 1.5 kg when one man weighing 60 kg is replaced by a new man. The new man weighs:
- A) 61.5 kg
- B) 70 kg
- C) 75 kg ✔
- D) 90 kg
Why: New = 60 + 10 × 1.5 = 60 + 15 = 75 kg.
The average of 5 numbers is 30. When one number is removed, the average of the rest is 28. The removed number is:
- A) 2
- B) 30
- C) 32
- D) 38 ✔
Why: 5 × 30 = 150 and 4 × 28 = 112, so the removed number is 150 − 112 = 38.
30 boys have an average of 50 marks and 20 girls have an average of 60 marks. The average of the whole class is:
- A) 54 ✔
- B) 55
- C) 56
- D) 52
Why: (30 × 50 + 20 × 60) ÷ 50 = (1,500 + 1,200) ÷ 50 = 2,700 ÷ 50 = 54.
A batsman scores 85 runs in his 15th innings and increases his average by 3. His average after the 15th innings is:
- A) 40
- B) 42
- C) 43 ✔
- D) 45
Why: 85 − 14 × 3 = 85 − 42 = 43. (Check: 14 × 40 + 85 = 645 = 15 × 43)
The average of 5 consecutive odd numbers is 25. The largest of them is:
- A) 27
- B) 29 ✔
- C) 31
- D) 33
Why: 25 is the middle number, so the numbers are 21, 23, 25, 27 and 29.
The average of three numbers is 24. Two of them are 16 and 35. The third number is:
- A) 21 ✔
- B) 24
- C) 25
- D) 19
Why: Sum = 3 × 24 = 72, so the third number = 72 − 16 − 35 = 21.
A is 5 years older than B, and the sum of their ages is 35 years. A's age is:
- A) 15 years
- B) 18 years
- C) 20 years ✔
- D) 25 years
Why: B = x, A = x + 5, so 2x + 5 = 35, x = 15 and A = 20.
The present ages of two brothers are in the ratio 3 : 4. After 6 years the ratio will be 4 : 5. The elder brother's present age is:
- A) 18 years
- B) 24 years ✔
- C) 20 years
- D) 30 years
Why: (3x + 6) ÷ (4x + 6) = 4 ÷ 5 gives 15x + 30 = 16x + 24, so x = 6; ages are 18 and 24.
A father is 4 times as old as his son. After 5 years he will be 3 times as old as his son. The father's present age is:
- A) 30 years
- B) 35 years
- C) 45 years
- D) 40 years ✔
Why: 4x + 5 = 3(x + 5) gives x = 10, so the father is 40.
The difference between the ages of two persons is 8 years now. After 10 years the difference will be:
- A) 18 years
- B) 8 years ✔
- C) 10 years
- D) 2 years
Why: The difference between two ages never changes.
A man's age 10 years hence will be twice his age 10 years ago. His present age is:
- A) 20 years
- B) 25 years
- C) 30 years ✔
- D) 40 years
Why: x + 10 = 2(x − 10) gives x + 10 = 2x − 20, so x = 30.
The average age of a husband and wife was 25 years when they married 4 years ago. Now, with one child, the average age of the family is 20 years. The child's age is:
- A) 2 years ✔
- B) 3 years
- C) 4 years
- D) 1 year
Why: Couple now = 2 × 25 + 2 × 4 = 58. Family total = 3 × 20 = 60, so the child is 60 − 58 = 2 years.
The average of 10, 20, 30, 40 and 50 is:
- A) 30 ✔
- B) 25
- C) 35
- D) 150
Why: 150 ÷ 5.
The average of the first 10 natural numbers is:
- A) 5.5 ✔
- B) 5
- C) 10
- D) 55
Why: 55 ÷ 10.
The average of the first 5 multiples of 3 is:
- A) 9 ✔
- B) 15
- C) 6
- D) 12
Why: (3+6+9+12+15) ÷ 5.
The average of 12 numbers is 25. Their sum is:
- A) 300 ✔
- B) 250
- C) 37
- D) 325
Why: 12 × 25.
The average of 4 numbers is 20. A fifth number 30 is added. The new average is:
- A) 22 ✔
- B) 25
- C) 24
- D) 21
Why: 110 ÷ 5.
The average of 5 numbers is 40. One is removed and the average of the rest is 35. The removed number is:
- A) 60 ✔
- B) 40
- C) 45
- D) 55
Why: 200 − 140.
The average of 6 numbers is 10. Each number is multiplied by 3. The new average is:
- A) 30 ✔
- B) 13
- C) 10
- D) 60
Why: Average also triples.
The average of some numbers is 10. Each is increased by 5. The new average is:
- A) 15 ✔
- B) 10
- C) 50
- D) 20
Why: Average rises by 5.
The average age of 30 students is 14. With the teacher included it becomes 15. The teacher's age is:
- A) 45 ✔
- B) 44
- C) 30
- D) 46
Why: 31 × 15 − 420.
The average weight of 8 people rises by 2.5 kg when a new person replaces one weighing 60 kg. The new person weighs:
- A) 80 kg ✔
- B) 62.5 kg
- C) 70 kg
- D) 85 kg
Why: 60 + 8 × 2.5.
The average of 3 numbers is 30. Two of them are 25 and 35. The third is:
- A) 30 ✔
- B) 40
- C) 20
- D) 35
Why: 90 − 60.
A batsman averages 40 in 10 innings. How many runs in the 11th to make the average 42?
- A) 62 ✔
- B) 42
- C) 52
- D) 82
Why: 462 − 400.
The average of the first 50 natural numbers is:
- A) 25.5 ✔
- B) 25
- C) 50
- D) 26
Why: (1 + 50) ÷ 2.
The average of 7 consecutive numbers is 20. The largest is:
- A) 23 ✔
- B) 20
- C) 26
- D) 22
Why: 17 to 23.
20 students average 60 and 30 students average 70. The combined average is:
- A) 66 ✔
- B) 65
- C) 64
- D) 68
Why: 3,300 ÷ 50.
A car goes at 40 km/h and returns at 60 km/h. The average speed for the trip is:
- A) 48 km/h ✔
- B) 50 km/h
- C) 45 km/h
- D) 52 km/h
Why: 2 × 40 × 60 ÷ 100.
5 children born 3 years apart have ages summing to 50. The youngest is:
- A) 4 years ✔
- B) 5 years
- C) 6 years
- D) 3 years
Why: 5x + 30 = 50.
A father is 30 years older than his son. In 5 years he will be twice the son's age. The son's present age is:
- A) 25 ✔
- B) 20
- C) 30
- D) 15
Why: S + 35 = 2(S + 5).
Two ages are now 4 : 5; after 5 years they will be 5 : 6. The younger is now:
- A) 20 ✔
- B) 16
- C) 25
- D) 15
Why: x = 5.
A mother is 3 times as old as her daughter; their ages total 48. The daughter is:
- A) 12 ✔
- B) 16
- C) 36
- D) 15
Why: 4x = 48.
Five years ago A was 20. Five years from now A will be:
- A) 30 ✔
- B) 25
- C) 35
- D) 20
Why: Now 25.
Average of A and B is 25, B and C is 30, A and C is 35. The average of A, B and C is:
- A) 30 ✔
- B) 90
- C) 35
- D) 25
Why: Sum = 180 ÷ 2 = 90.
The average of 11 numbers is 50. The first six average 49 and the last six average 52. The sixth number is:
- A) 56 ✔
- B) 50
- C) 52
- D) 54
Why: 294 + 312 − 550.
The average of the first 10 odd numbers is:
- A) 10 ✔
- B) 11
- C) 9
- D) 20
Why: Sum 100 ÷ 10.
The average of the first 5 even numbers is:
- A) 6 ✔
- B) 5
- C) 10
- D) 8
Why: (2+4+6+8+10) ÷ 5.
The average of 2, 4, 6 and 8 is:
- A) 5 ✔
- B) 4
- C) 6
- D) 20
Why: 20 ÷ 4.
The average of x, x + 2 and x + 4 is:
- A) x + 2 ✔
- B) x + 4
- C) 3x
- D) x
Why: Middle term.
If the average of 5 numbers is 0, their sum is:
- A) 0 ✔
- B) 5
- C) 1
- D) Cannot say
Why: 5 × 0.
10 years ago a family of 4 had an average age of 24. With the same members, the average now is:
- A) 34 ✔
- B) 24
- C) 28
- D) 44
Why: Everyone is 10 years older.
The average of a and b is 20, and c is 50. The average of a, b and c is:
- A) 30 ✔
- B) 35
- C) 25
- D) 40
Why: (40 + 50) ÷ 3.