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⑥56×23+44×23 =(56+44)×23 =100×23 =2300
⑦178×45-45×78 =(178-78)×45 =100×45 =4500 ⑧34×99+34 =34×(99+1) =34×100 =3400
⑨78×12+21×12+12 =(78+21+1)×12 =100×12 =1200 4、除法 ①3000÷125÷8 =3000÷(125×8)=3000÷1000