The average of 5 numbers, arranged in a row, is 309. The average of the first two of these numbers is 431 and the average of the last two of these numbers is 231.5. What is the value of the number at the center of the row?

If 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?

The average of 5 numbers is 27. If one number is excluded, the average becomes 25. The excluded number is: 

The average of 8 numbers is 27. If each of the numbers is multiplied by 8, find the average of new set of numbers.

The average score of top 6 batsmen of Indian cricket team in a match is 46. If the 7th batsman is included, the average becomes 50. If the 8 batsman comes and scores 34 runs, then find the ratio of the average scores of top 6 and top 8 batsmen.

A man bought 13 articles at Rs. 70 each, 15 at Rs. 60 each and 12 at Rs. 65 each. The average price per article is 

Average of 21 number is 36. If the average of first 12 numbers is 15, then find the average of remaining 9 number?

The average monthly salary of the workers in a workshop is Rs. 8,500. If the average monthly salary of 7 technicians is Rs.10,000 and average monthly salary of the rest is Rs. 7,800, the total number of workers in the workshop is