估算.71×2≈ 49×3≈ 102×6≈ 25÷3≈ 63÷5≈ 46÷5≈
58×52+58×50﹣58×2.
用简便方法计算.201×42 47×48+48×53137×46﹣37×46 125×32×25.
脱式计算6.47×4.5+3.53×4.5 0.25×8×40×0.125.
用简便方法计算下面各题.3.8×6.7+3.3×3.8 1.28×0.29﹣0.29×0.28 101×4.8 56×12.5.
53×99.