The average of 12 number is 42. If a 13th number is added, then the average becomes 44. What is the 13th number?

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. 

The average of eleven numbers is 68. The average of the first numbers is 78 and that of the next four number is 63. The 9^th number is two time the 11^th number and the 10^th number is 4 less than the 11^th number. What is the average of the 9^th and 11^th numbers?

A cricketer had a certain average of runs for his 64 innings. In his 65th innings, he is bowled out for no score on his part. This brings down his average by 2 runs. His new average of runs is: 

The average of 10 numbers is calculated as 15. It is discovered later on that while calculating the average one number, namely 36, was wrongly read as 26. The correct average is: 

The average of 24 number is 65. The average of first 11 number is 67 and the average of last 10 number is 70. If the 12^th Number is 13 less than the 13^th number , and the 14^th number is  one more than the 13^th number, then the average of 12^th and 14^th number is:

There are 100 students in 3 sections A, B and C of a class. The average marks of all the 3 sections was 84. The average of B and C was 87.5 and the average marks of A is 70. The number of students in A was.