估算:49×101 196×39 203×38 396×102 89×92 98×69
39\u00d7101\u548c89\u00d7101-89\u7684\u7b80\u4fbf\u8ba1\u7b9739x101=39x(100+1)=3900+39=3939
89x101-89=89x(101-1)=89x100=8900
610
49×101≈5000; | 196×39≈8000; | 203×38≈8000; |
396×102≈40000; | 89×92≈8100; | 98×69≈7000. |