If (a + b): (b + c): (c + a) = 5: 6: 9 and a + b + c = 10. What is the value of c?

The average of a,b,c is 20 and that of b,c,d is 25, if d=30, then the value of a is-

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.

The average expenditure of a man for the first five months of a year is Rs. 5,000 and for the next seven months is Rs. 2,300 during a year. His average monthly expenditure is : 

Of the three numbers whose average is 60, the first is one-fourth of the sum of the whole number. The first number is: 

The average age of five girls is 11. The oldest among them is 15 years old. What is the average age of the others?

The average of 5 consecutive natural numbers is M. If the next three natural numbers are also included, how much more than M will the average of these 8 numbers be? 

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: