二年级数学上册第一单元《巧算》课件2沪教版五四制.pptx

巧算,口算1：,6 + 7 =,16+ 7 =,36+ 7 =,56+ 7 =,13,23,43,63,86+ 7 =,93,一个加数不变，另一个加数增加几，和就增加几。,一个加数不变，另一个加数减少几，和就减少几。,+10,不变,+10,+20,不变,+20,8 + 3 =,18 + 13 =,28 + 33 =,48 + 43 =,11,两个加数一共增加几，和就增加几。,31,61,91,两个加数一共减少几，和就减少几。,+10,+10,+20,+10,+20,+30,填一填,22+ 19 = 41,22+ = 61,36+ 29 = 65,46+ = 85,35+ 38 =73,+ 38 =83,44+ 17 =61,+ 37 =81,（1）,（2）,（3）,（4）,39,+20,+20,+10,+20,+10,39,45,44,口算2：,81- 6=,75,71- 6 =,51- 6 =,21- 6 =,65,45,15,减数不变，被减数减少几，差就减少几。,减数不变，被减数增加几，差就增加几。,-10,不变,-10,-20,不变,-20,-30,不变,-30,口算： 26+18= 25+19= 24+20=,44,44,44,哪题算得最快？,20,+1,15,-1,85,43,93,+2,-2,40,15,55,+2,-2,口算： 95-28= 96-29= 97-30=,67,67,67,哪题算得最快？,30,20,+1,+1,74,54,20,+3,+3,59,39,20,+1,+1,68,48,30,+5,+5,49,19,填一填,3814 =, =,40,52,52,12,6431 =, =,65,95,95,30,5119 =, =,52,32,32,20,4932 =, =,47,17,17,30,巧算,口算1：,6 + 7 =,16+ 7 =,36+ 7 =,56+ 7 =,13,23,43,63,86+ 7 =,93,一个加数不变，另一个加数增加几，和就增加几。,一个加数不变，另一个加数减少几，和就减少几。,+10,不变,+10,+20,不变,+20,8 + 3 =,18 + 13 =,28 + 33 =,48 + 43 =,11,两个加数一共增加几，和就增加几。,31,61,91,两个加数一共减少几，和就减少几。,+10,+10,+20,+10,+20,+30,填一填,22+ 19 = 41,22+ = 61,36+ 29 = 65,46+ = 85,35+ 38 =73,+ 38 =83,44+ 17 =61,+ 37 =81,（1）,（2）,（3）,（4）,39,+20,+20,+10,+20,+10,39,45,44,口算2：,81- 6=,75,71- 6 =,51- 6 =,21- 6 =,65,45,15,减数不变，被减数减少几，差就减少几。,减数不变，被减数增加几，差就增加几。,-10,不变,-10,-20,不变,-20,-30,不变,-30,口算： 26+18= 25+19= 24+20=,44,44,44,哪题算得最快？,20,+1,15,-1,85,43,93,+2,-2,40,15,55,+2,-2,口算： 95-28= 96-29= 97-30=,67,67,67,哪题算得最快？,30,20,+1,+1,74,54,20,+3,+3,59,39,20,+1,+1,68,48,30,+5,+5,49,19,填一填,3814 =, =,4