Find the value of given equations

The value of is closest to 

The sum of a positive integer and its square is 2450. The positive integer is : 

How many perfect squares lie between 120 and 300? 

The smallest 4- digit number which is a perfect square is 

The smallest number that must be subtracted from 1000 to make the resulting number a perfect square is 

The largest number of five digits, which is a perfect square is 

The smallest positive integer n for which 864 x n is a perfect cube, is: