(1)272-44+85 =228+85 =313;
(2)230-130÷10 =230-13 =217; | |
(3)144+(57-12)×2 =144+45×2 =144+90 =234;
(4)250×15×4 =(250×4)×15 =1000×15 =15000; | |
(5)99×45+45 =45×(99+1) =45×100 =4500; | |
(6)17×23-23×7 =23×(17-7) =23×10 =230;
(7)289-125-75 =289-(125+75) =289-200 =89;
(8)25×16 =25×4×4 =100×4 =400; | |
(9)3200÷4÷25 =3200÷(4×25) =3200÷100 =32. |