Q1. The mean of 100 items was 46. Later on it was discovered that an item 16 was misread as 61 and another item 43 was misread as 34. It was also found that the number of items was 90 and not 100. Then what is the correct mean?
(a) 50
(b) 50.7
(c) 52
(d) 52.7
Q2. The average of seven numbers is 18. If one of the number is 17 and if it is replaced by 31, then the average becomes:
(a) 21.5
(b) 19.5
(c) 20
(d) 21
Q3. In an exam, the average marks obtained by the students was found to be 60. After omission of computational errors, the average marks of 100 candidates had to be changed from 60 to 30 and the average with respect to all the examinees came down to 45 marks. The total number of candidates who took the exam, was
(a) 200
(b) 210
(c) 240
(d) 180
Q4. The average to 10 items was found to be 80 but while calculating, one of the items was counted as 60 instead of 50. Then the correct average would have been:
(a) 69
(b) 79.25
(c) 79
(d) 79.5
Q5. The average of 9 integers is found to be 11. But after the calculation, it was detected that, by mistake, the integer 23 was copied as 32, while calculating the average. After the due correction is made, the new average will be
(a) 10
(b) 9
(c) 10.1
(d) 9.5
Q6. The average marks secured by 36 students was 52. But it was discovered that an item 64 was misread as 46. What is the correct mean of marks?
(a) 54
(b) 53.5
(c) 53
(d) 52.5
Q7. A student finds the average of 10, 2 digits numbers. If the digits of one of the numbers is interchanged, the average increases by 3.6. The difference between the digits of the 2 digits number is
(a) 4
(b) 3
(c) 2
(d) 5
Q8. The average marks obtained by the students in 6 subject is 88. On subsequent verification it was found that the marks obtained by him in a subject was wrongly copied as 86 instead of 68. The correct average of the marks obtained by him is:
(a) 87
(b) 86
(c) 85
(d) 84
Q9. Average age of 5 boys is 16 yr, of which that of 4 boys is 16 yr 3 months. The age of the 5th boy is
(a) 15 yr
(b) 15 yr 6 months
(c) 15 yr 4 months
(d) 15 yr 2 months
Q10. The average of marks of 14 students was calculated as 71. But if was later found that the marks of two students has been wrongly entered as 42 instead of 56 and of another as 74 instead of 32. The correct average is:
(a) 67
(b) 68
(c) 69
(d) 71
Q11. The average of a collection of 20 measurements was calculated to be 56 cm. But later it was found that a mistake had occurred in one of the measurements which was recorded as 64 cm., but should have been 61 cm. The correct average must be:
(a) 53 cm
(b) 54.5 cm
(c) 55.85 cm
(d) 56.15 cm
Q12. The mean of 50 observations was 36. It was found later that an observation 48 was wrongly taken as 23. The corrected (new) mean is:
(a) 35.2
(b) 36.1
(c) 36.5
(d) 39.1
Q13. The average of marks in Mathematics for 5 students was found to be 50: Later, it was discovered that in the case of one student the marks 48 were misread as 84. The correct average is:
(a) 40.2
(b) 40.8
(c) 42.8
(d) 48.2
Q14. The average age of eleven cricket players is 20 years. If the age of the coach is also included, the average age increased by 10%. The age of the coach is:
(a) 48 years
(b) 44 years
(c) 40 years
(d) 36 years
Q15. The mean of 9 observation is 16. One more observation is included and the new mean becomes 17. The 10th observation is:
(a) 9
(b) 16
(c) 26
(d) 30