To find the square of any 3 Digit Number there is a small process and you can easily solve the questions.
We will learn by the example that is given in the image
Take any number as we take 367 in this example
There is a few steps
Step-1 : Take a base number near of given number
Like we will take 350 as a number
Step-2 : now our given number is 367 and base number is 350 . So the difference between these is 17
In step 2 we add 17 in 367
i.e. 367+17=384
Step-3 : in step 3 we will multiply 350 and 384
i.e. 350*384=1,34,400
Step-4 : in step add the square of difference of base number and given number
In our case 17 is difference
So square of 17 is 289
i.e. 1,34,400+289=1,34,689
So 1,34,689 is the square of 367
Is really easy just practice at home and get perfect
Best of luck
Thank you