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@Humpleupagus @Stahesh

X^2 = X*X

( A + B ) * ( A - B ) = A^2- B^2

56 * 54 = ( 55 +1 ) * ( 55 - 1 ) =

(55 +1 ) * ( 55 -1 ) = 55^2 -1^2

(A+B)*(A+B ) = A^2 + 2*A + B^2

(55)^2 = (50+5)^2

(50+5)^2 = 50^2+2*50*5+5^2

(50+5)^2 = 2500 + 500 + 25 = 3025

I am too lazy to show the proof but another shortcut is
(10X+5)^2 =(x+1)*(x)*10+25

55^2 = (6*5)*10+25 = 3025

so 56*54 = 3025 -1 = 3024

Very easy to do in your head extra steps are just to show for new learners