脱式计算,能简算的要简算:
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| (1)46.5×99+46.5 =46.5×(99+1) =46.5×100 =4650 (2)12.5÷2.5÷0.4 =12.5÷(2.5×0.4) =12.5÷1 =12.5 (3)2.6×1.9÷2.6×1.9 =2.6÷2.6×1.9×1.9 =1×1.9×1.9 =3.61 (4)(7.7+1.54)÷0.7 =9.24÷0.7 =13.2 (5)10.8÷[(4.62-1.92)×4] =10.8÷[2.7×4] =10.8÷10.8 =1 (6)2.6×(2.139÷9.3×6.2) =2.6×(0.23×6.2) =2.6×1.426 =3.7076 |
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后,新数比原数少138.6,原数是多少?