估算.45×29≈ 32×49≈ 22×38≈ 52×68≈69×30≈ 89×30≈ 79×20≈ 42×68≈
400﹣98=
用简便方法计算:5.6×0.38+0.56×4.7+0.056×15.
用简便的方法计算下面各题4,5×0.9+5.5×0.9 7.69×101 2.5×(7.2×0.04)72×l.25 0.26×10.1﹣0.26×0.1 0.25+39×0.25.
简便计算.1﹣().
①(23+27)×(77+73)×25.②19×27+190×5+19×23.③23×2×24+25×4×2+27×1×8+25×8×1.④1250×32×25.