Bạn tham khảo :
Bài $4$ :
$f,$
$499 . 12 = (500 - 1) .12= 12.500 - 12 = 6000 - 12 = 5988$
$g,$
$601 . 42 = (600+1) . 42 = 42 . 600 + 42 = 25200 + 42 = 25242$
$h$
$199 . 41 = (200 - 1) . 41 = 200 . 41 - 41 = 8200- 41 = 8159$
Bài $5$
$c,$
$15 . 16 . 125 = 15 . (16 :4) . (125 . 4) = 15 . 4 . 500 = 15 . 2000 = 30000$