已知:∠1=75°,∠AOB=130°,求:∠2=?
计算下面各题,能用简便方法的用简便方法计算 8.42+8.46+8.54+8.58= 51.26﹣8.76﹣1.24= 9.5+4.85﹣6.23=125×7×32= 19×36﹣36×12= (124﹣85)×12÷26=
简便计算0.389×4×0.25 10.1×7.8 6.37×3.02+6.98×6.37.
×15+÷.
简便计算.①7.7×7+7.7×2+7.7 ②87.3×45+10.7×45+2×45 ③(2.5+2.5+2.5+2.5)×2.5×8.
43.87×2.65﹣26.5×5.613=( 265 )