类型一:(连加运算,把相加得整十、整百的数凑到一起先求和) 827+15+85 =827+(15+85) =827+100 =927 119+81+259 =200+259 =459 368+29+32 =(368+32)+29 =400+29 =429 类型二:(连减运算,把后两个减数相加得整十、整百的数用小括号括起来先求和,最后求差) 702-54-46 =702-(54+46) =702-100 =602 600-137-63 =600-(137+63) =600-200 =400 645-180-245 =(645-245)-180 =400-180 =220 类型三:(连乘运算,把相乘得整十、整百的数凑到一起先求积) 25×14×4 =25×4×14 =100×14 =1400 125×19×8 =125×8×19 =1000×19 =19000 250×13×4 =250×4×13 =1000×13 =13000 28×4×25 =25×4×28 =100×28 =2800 13×125×3