With out calculating the cubes find the value

Question

55³-25³-30³

without calculating the cubes find the value

Answer 1

55^3-25^3 -30^3

(a^3-b^3)=(a-b)(a^2+ab+b^2)

Here a=55, b=25

55^3-25^3=(55-25)(55^2+55*25+25^2)

=30*(3025+1375+625)

=30*5025

Now

55^3-25^3-30^3=30*5025-30^3

Take 30 common

= 30(5025-900)

=30*4125

=123750