Maths - Average 1. Find the average of first 50 natural numbers. a. 50 b. 50.5 c. 60 d. None of these 2. Find the average of first 20 multiples of 7. a. 140 b. 50.5 c. 73.5 d. None of these 3. The average of four consecutive even numbers is 29. The least number of these numbers is a. 26 b. 28 c. 30 d. None of these 4. The average of 25 results is 18. The average of first twelve of them is 14 and that of last 12 is 17. The thirteenth result is a. 78 b. 79 c. 80 d. None of these 5. The average of all odd numbers up to 100 is a. 49 b. 50 c. 100 d. None of these 6. The average of five consecutive odd numbers is 59. What is the difference between the highest and lowest number? a. 2 b. 4 c. 6 d. 8 7. The mean of 12,22,32,42,52,62,72 is a. 10 b. 20 c. 30 d. 40 8. The average marks of three batches of 55, 60 and 45 students respectively is 50, 55 and 60, then the average marks of all the students is a. 53.33 b. 54.68 c. 55 d. None of these 9. The average of 50 numbers is 30. If two numbers, 60 and 48 are discarded, then the average of remaining numbers is a. 27 b. 29 c. 30 d. None of these 10. The average age of a class of 35 students is 14.8. A new student joins the class and the average becomes 14.9 years. The age of new comer is a. 18.4 b. 16.3 c. 17.4 d. None of these 11. Of the four numbers, whose average is 60, the first is one-fourth of the sum of the last three. The first number is a. 15 b. 45 c. 48 d. 60.25 12. If the average mean of 49 numbers is calculated, it is 35. If each number is increased by 5, then mean of new numbers is a. 35 b. 40 c. 50 d. None of these 13. The mean of 50 observations was 36. It was found later that an observation 48 was taken as 23. The correct new mean is a. 35.2 b. 36.1 c. 36.5 d.39.1 14. The average monthly salary of A, B and C is Rs. 4000 and that of B, C and D is Rs. 5000. The actual salary of A is Rs. 2750. The actual salary of D is a. 5750 b. 5870 c. 5780 d. None of these 15. There are 30 students in a class. The average age of first 10 students is 12.5 years. The average age of next 20 students is 13.1 years. The average age of the students of whole class is a. 12.5 b. 12.5 c. 12.8 d. 12.9 16. The average weight of a class of 24 students is 35 kg. If the weight of the teacher be included, the average rises by 400g. The weight of the teacher in kg is a. 45 b. 50 c. 53 d. 55 17. A batsman average score for a number of innings was 21.75 per innings. In the next three innings he scored 23, 34 and 37 runs and his average for all the innings was raised by 1.25. How many innings in all did he play? a. 20 b. 23 c. 26 d. 29
18. The average salary per head of all the workers of an institution is Rs. 600. The salary per head of 12 officers is Rs. 4000 and the average salary of the rest is Rs. 560. The number of staff members in the institution is a. 1000 b. 1032 c. 666 d. 1200 19. A cricketer has a certain average of 10 innings. In the eleventh innings, he scored 108 runs, thereby increasing his average by 6 runs. His new average in runs is a. 48 b. 52 c. 55 d. 60 20. The average age of students of a class is 15.8 years. The average age of boys in the class is 16.4 years and that of the girls is 15.4 years. The ratio of number of boys to the number of girls in the class is a. 1:2 b. 2:3 c. 3:4 d. 4:5 21. The average age of 10 boys in a class is 12 years. The average age of the 10 boys and their teacher is 15. What is the age of the teacher? a. 45 b. 40 c. 35 d. None of these 1 1 1
22. The sides of a triangle are in the ratio2 : 3 : 4. If the perimeter of the the triangle is 52 cm, the length of the smallest side is a. 24 b. 18 c. 12 d. 9 23. The average marks of 50 students of class is 36 and that of 100 students of the other class is 33. The average marks of students of both classes taken together is a. 33 b. 34 c. 34.5 d. 35 24. In a class there are 20 boys whose average age is decreased by 2 months when 1 boy of 18 years old is replaced by a new boy. Find the age of new boy a. 14 years,8 month b. 14 years,6months c. 15 years d. None of these 25. A student obtains 75%, 80% and 85% in three subjects. If the marks of another subject are added, then his average cannot be less than a. 60% b. 65% c. 80% d. 90% 26. 3 year ago, the average age of 5 members of a family was 17 years. Now the average age of 6 members remains same if a child is born within this period. What is the present age of new born? a. 1yr b. 1.5 yr c. 2 yr d. 2.5 yr 27. The average age of a husband and wife was 27 years when they married 4 year ago. The average age of the husband, wife & a new born child is 21 years now. The present age of the child is a. 3.2 yr b. 3 yr c. 2 yr d. 1 yr 28. The average of 5 numbers is 140. If a number is excluded, the average of rest 4 numbers is 130, find the excluded number. a. 180 b. 170 c. 160 d. 190 29. The average of five numbers is 7. When three new numbers are included, the average of the eight numbers becomes 8.5. The average of the three new numbers is a. 9 b. 10.5 c. 11 d. 11. 5 30. The average temp. of the first 4 days of a week was 370 C and that of the last 4 days of the week was 410 C. If the average temperature of whole week was 390 C, the temperature of the fourth day was a. 380 C b. 38.50 C c. 390 C d. 400 C 1. d 6. d 11. c 16. a 21. a 26. c
2. c 7. b 12. b 17. b 22. c 27. d
3. a 8. b 13. c 18. b 23. b 28. a
4. a 9. b 14. a 19. a 24. a 29. c
5. b 10. a 15. d 20. b 25. a 30. c