Squaring Trick of two Digit Number containg 5 in ones place

Suppose the Number is 25

we have to squrare it 

we take the tens digit ie 2 and multiply it by number,  1 more than it 

2*(2+1)=2*3=6

and the square of 5 is 25 

so the square of 25 is  = 6/25=625

Similarly

square of 65 is 6*(6+1)/25=6*7/25=4225

square of  115= 11*12/25=13225


practice it to be perfect