3．估算．
| 603×21≈ | 399×42≈ | 538×48≈ |
| 89×202≈ | 139×48≈ | 302×51≈ |
2．口算：
0 162476 162484 162490 162494 162500 162502 162506 162512 162514 162520 162526 162530 162532 162536 162542 162544 162550 162554 162556 162560 162562 162566 162568 162570 162571 162572 162574 162575 162576 162578 162580 162584 162586 162590 162592 162596 162602 162604 162610 162614 162616 162620 162626 162632 162634 162640 162644 162646 162652 162656 162662 162670 199269
| 18×3= | 60×6= | 35×4= | 72×2= |
| 15×30= | 17×40= | 190×3= | 95×4= |