This tricks will teach you how to calculate in mind the square product of a two-digit number ending with 5 (can be used for 3-digit numbers, but will be hard to do in mind). If you have a number like N5 (15, 25, 35, 45, etc.), then the square product of the number is (N x (N+1))25, in which “25” is appended to (N x (N=1)).

For example:

15² = (1 x (1+1))25 ==> 225

25² = (2 x (2+1))25 ==> 625

35² = (3 x (3+1))25 ==> 1225

45² = (4 x (4+1))25 ==> 2025

…

95² = (9 x (9+1))25 ==> 9025

Have fun!