27 . 19 + 73 . 20
= 27 . 19 + 73 . 19 + 73
= 19 . (27 + 73) + 73
= 19 . 100 + 73
= 1900 + 73
= 1973
25254 . 58 + 21 . 508
= 25254 . 50 + 25254 . 8 + 21 . 500 + 21 . 8
= 25254 . 50 + 25254 . 8 + 210 . 50 + 21 . 8
= (25254 . 50 + 210 . 50) + (25254 . 8 + 21 . 8)
= [50 . (25254 + 210)] + [8. (25254 + 21)]
= (50 . 25464) + (8 . 25275)
= 1273200 + 202200
= 1475400
(9 - 8 - 7 -... - 2 -1) . (500.9 - 250.18)
= (9 - 8 - 7 -... - 2 -1) . (4500 - 4500)
= (9 - 8 - 7 -... - 2 -1) . 0
= 0