第一类:加 65+73+135 357+288+143 272+68+28 =65+135+73 =357+143+288 =272+28+68 =200+73 =500+288 =300+68 =273 =788 =368 129+235+171+165 17+145+23+35 999+99+9+3 =129+171+235+165 =17+23+145+35 =999+1+99+1+9+1 =300+400 =40+180 =1000+100+10 =700 =220 =1110 第二类:减 400-256-44 517-53-47 284-159-41 =400-(256+44) =517-(53+47) =284-(159+41) =400-300 =517-100 =284-200 =100 =417 =84 258-42-16 545-167-145 478-47-178 =258-(42+16) =545-145-167 =478-178-47 =258-58 =400-167 =300-47 =200 =233 =253 344-(144+37) 236-(177+36) =344-144-37 =236-177-36 =200-37 =236-36-177 =163 =200-177 =23 第三类:乘 8×(125×13) (250×125)×(4×8) =8×125×13 =250×125×4×8 =1000×13 =250×4×125×8 =13000 =1000×1000 =1000000 88×125 72×125 125×64×25 =11×8×125 =9×8×125 =125×8×2×4×25 =11×1000 =9×1000 =1000×2×100 =11000 =9000 =200000 42×125×8×5 25×4×88×125