小学数学-三年级--人教版三年级数学下册笔算乘法(一)课件-维语.ppt

?????????? ??????? ????????(1)1 1.??????? ????????:12 ×20= 12 ×30= 24 ×10=20 ×32= 21 ×40= 18 ×20= 2.??????? ????????:24 ×3= 78 ×8= 12 ×2=2 ?????? ???????? ?????? 12????????? ??? ??????? 24?????.?????? ????? ??? ????????????? ????? ????? ????? ??????????? ??????.3 24×10＝24024×2＝48240 + 48＝28824×12＝???????? ?????? ?????????: ???????? ?????? ?????????: 20×12=2404×12=48240+48=288288?????? ?????4 ?????? ????? ????????? ????????? ??????? ????????5 ??????? ???????? 2 4× 1 26 2 4 × 1 2 4 8……24×2 ??? ??????????7 2 4× 1 2 4 8……24×2??? ??????????……24×10 ?????????? ???428 2 4× 1 2 4 8……24×2??? ?????????? 2 4 ……24×10??? ?????????? 2 8 8 （?????? ?????????? 0?? ?????????）9 ??? ??????? ????? ????? ??????? ????? ?????????? ??? ??????? ???????? ??????: 1.?????? ????? ??????? ????????????? ?????? ????????? ?????? ???????? ??????? ?????? ??????? ???????? ????????? ????? ??????? ????????????? ?????? ???????? ????? ????? ???????.2.?????? ????? ??????? ????????????? ?????? ???????? ???????? ??????? ?????? ??????? ???????? ????????? ????? ??????? ????????????? ?????? ???????? ????? ????? ???????.3.??? ??????? ?? ????? ???????? ??????????? ????? ?????? ???????? ???-???? ???????.10 23×13= 33×31= 43×12= 11×25=11 32×22メ31 × 32メ9 33 1×3 26 29 9 213 ×12メ 1 3× 1 22 61 31 5 6 11×25√ 3 2× 2 26 42 43 0 4=3047049 33 1×3 26 21 5 5=155992 1 3× 1 22 61 31 6 6=166156 1 1× 2 55 52 22 7 5=275????? ??????: 3 2 × 2 26 46 47 0 412 14×12＝ （????）??? ??? ?????? 12???? ??? ??? ???.???????? ????????14???? ??? ??? ??????????????? ????? ???? ??? ??? ????13 12×12＝ （????）144???????? ?????????????? ???????12 ????? ??????.?????? ????? ???? ????? ????? ?????????? ??????? 12???? ???.14 ?????? ????? 41×21＝ 32×12＝23×13＝ 22×14＝32×12＝ 21×34＝ ???? ????? ???????15