how to find square root of a number ending with 2,3,7,8? square root will always be an irrational number,is there any trick to find that number quickly?

Well there is one method for finding the approximate value of square roots. Let me give you an example
Suppose you want to find the square root of 42. Then you have to find the nearest squares previous and next to the given number which are 36 and 49. So 42 is 6 away from 36 and difference between 36 and 49 is 13. So value of 42 is 6+(6/13) i.e. 6.46 approx. Hope this helps!

we cant define any square root of number by taking last two digits.. we had some older methods as we know how to solve the number... as subhadeep said finding number near to them can be some solution but if its a large digit number like 7 digit number etc... finding the nearest square root number will be definitely difficult..... i had searched some methods about it... hope it may work for you http://www.vedantatree.com/2013/03/vedic-math-square-roots.html open this link it may work for you

Well there is one method for finding the approximate value of square roots. Let me give you an example
Suppose you want to find the square root of 42. Then you have to find the nearest squares of the number previous and next to it which are 36 and 49. So 42 is 6 away from 36 and difference between 36 and 49 is 13. So value of 42 is 6+(6/13) i.e. 6.46 approx. Hope this helps!