用递等式计算．
| 68×35-408÷24 |  ÷[ -（ + ）] | 18-10.4÷（6.2-4.9） |
口算．
| 800-250= | 30×40= | 8100÷900= | 10-0.98= | 105÷7= | 560+770= |
| 0.25×0.4= | 6.3÷0.07= | 0.64÷8= | 8.85×10= | 4.73+0.7= |  = |
 = |  = |  = | 3.6× = | 8×1.36×1.25= | 7.2×2.8+2.8×0.8= |
直接写出得数．
| 2.05+3.6= | 5-1.34= | 36×11= | 50×60= |
| 32+3.15= | 1.23-0.9= | 4×17×25= | 125×8+5= |