Find the sum of 30²+31²+32²+________+80²

What value will come in place of question mark (?) in the questions given below?

(4425÷25) ×(8.5×16) = ?

A rational number between $${3\over4} $$ and $${3\over8} $$ is :

The number will be, whose square is equal to the difference between the squares of 975 and 585, is:

A number is divided by 6 and 5 is added to this quotient Again sum is divided by 9 and the quotient obtained is 1. Find the number.

The difference between the greatest and least five-digit numbers formed by the digits 2,5,0,6,8 is (repetition of digits are not allowed) 

If the product of four consecutive natural numbers increased by a natural number p, is a perfect square; then the value of p is: 

Amit ranked 7th from the top and 26th from the bottom in his class. How many students are there in the class?