They way I would do it other than with a calculator would be 27 x (90 - 0.5) which is the same as 27 x 89.5 => 27 x 90 - 27 x 0.5 27 x 90 is (3 x 9) x 90 or 3 x 9 x 90 9 x 90 = 810 3 x 810 = 2430 Then subtract 27 x 0.5, or 27 / 2 2430 - 27 / 2 => 2430 - 13.5 = 2416.5
