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?

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?

In a primary school 96 students are studying. Their average weight is 30 kg. If a student shift to another school the average weight is increased by 200 gm. Find the weight of the student who shifted from the school.

In a class, there are 30 girls and 15 boys and total average weight of class is $$47{7\over15}$$ kg. The total average weight of boys is 58 kg. Find the approximate average weight of girls. 

The average weight of A, B, and C is 52 kg. If the average weight of B and C is 44 kg and that of C and A is 46 kg, then what will be the weight of C?

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

In a year, the average expenditure of a family for the first 3 months, next 4 months and last 5 months is Rs 8400 per month, Rs 10080 per month, Rs 10608. Monthly and annual savings are Rs. 8640. If so, what is the average monthly income of this family?