简便计算
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| ①23.1-(12.1-2.46 ) =23.1-12.1+2.46 =11+2.46 =13.46 ②14.35+3.98+2.65 =(14.35+2.65)+3.98 =17+3.98 =20.98 ③12.5-8.14-1.86 =12.5-(8.14+1.86) =12.5-10 =2.5 ④125×56 =125×8×7 =1000×7 =7000 ⑤56×75+44×75 =75×(56+44) =75×100 =7500 ⑥101×43-43 =(101-1)×43 =100×43 =4300 |
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后,新数比原数少138.6,原数是多少?