Solve the square of 25, in a jiffy. Answer : 625
Another one: square of 35. Answer : 1225.
How it is done ?
25 x 25 . The last two digits of the product will always be 25 ( as 5 x 5 =25). The initial digits are obtained by multiplying 2 x 3 [ i.e. n (n+1) ].
Try it and see if you can square these numbers in a couple of seconds.
65, 75, 95.....