19．用简便方法计算下面的题目．
| 32×250 | 48×125 | 9×25×8 | 36×250 |
18．列竖式计算．
| 375×15 | 380×25 | 604×26 | 503×19 |
| 280×30 | 23×802 | 67×189 | 145×48 |
17．直接写得数．
0 158625 158633 158639 158643 158649 158651 158655 158661 158663 158669 158675 158679 158681 158685 158691 158693 158699 158703 158705 158709 158711 158715 158717 158719 158720 158721 158723 158724 158725 158727 158729 158733 158735 158739 158741 158745 158751 158753 158759 158763 158765 158769 158775 158781 158783 158789 158793 158795 158801 158805 158811 158819 199269
| 300×70= | 12×400= | 60×800= | 40×200= | 10×560= |
| 3×120= | 32×30= | 210×4= | 24×100= | 20×500= |