Squaring a no ending with 5

In this post,let s learn how to square a number that ends with the digit '5'.

Using examples to learn a method is always easy, so let s consider the squaring of the no '45'.

For all the nos ending with 5, the squared resultant no will have 25 as its last 2 digits. So, resultant must in the pattern _____25, what comes in the blank is calculated as follows. Remove the '5' from '45', we are left with '4', multiply it with its consecutive no, being '5', which gives 4*5=20. This '20' is filled in the above blank, hence giving the resultant to be 2025 !!!

Another example : 75

Pattern : ____ 25

7*8=56, hence resultant would be 5625.

Squaring a 2 digit number

The basis of this short cut to find a square of any 2 digit no is the algebraic equation

(a+b)^2 = a^2 + 2ab + b^2

For eg : If the no 43 has to be squared, then
(40+3)^2 = 40^2 + 2*40*3 + 3^2

Since the first part 40^2 can be easily resolved, adding up of the RHS of the equation gives the resultant.
I believe an addition always comes to aid better than a multiplication in the last few crucial moments of the exams !