四年级数学简便运算(含答案)

1、Ncx Dote FerSE0THRRII1Vouvin 邳echEzothn知识梳理简便运算教学重、难点作业完成情况典题探究(1) 75 X 45+17 X 25(2) 599996 + 49997 + 3998 + 407 + 89(3) (48 X 75 X 81) + ( 24 X 25 X 27)(4) 137 +4+25耐心细心责任心演练方阵(1)乘法交换律:38X 25X4ax b= bx a42X 125X 8A档(巩固专练)乘法结合律：(axb) xc = ax (bxc)25X 17X4(25X125) X (8X 4)49X4X538X 125X 8X 3(125X 25

2、)X 45 X 289X 2(125X 12) X 8125X (12X4)(2)乘法交换律和结合律的变化练习125X64125X 8844X25125 X 2425X 28(3)加法交换律:357 + 288+ 143a+ b= b+a加法结合律：(a+b) +c = a+ (b + c)158 + 395+ 105167+289+33129+ 235+ 171 +165378 +527+73169+ 78+2258+39+42+61138+ 293+62 + 107(4)乘法分配律:(80 + 4) X2525X (40+ 4)15X (20+ 3)(a+b) xc=axc+bxc(20+

3、 4) X 25(125+ 17) X 8r(5)乘法分配律正用的变化练习：36X325 >4139 M 01125 >88201 X24(6)乘法分配律反用的练习：34X 72+34X 2835X 37 + 65X 3785X 82+85X 1825X 97+25X 376X 25+25 X 24(7)乘法分配律反用的变化练习：38X29+3875X299+7564 X 199+ 64(8) 125 X ( 17 X 8) X 4375 X 480 + 6250 X 4813 X 99(9) 25 X 16 X125(10) 75000 + 125 + 156) 7900 +4+

4、25B档（提升精练）1)67 X 21+ 18 X 21 + 85792) 321 X 81 + 321 X 193)222222 X9999994) 333333 X 3333335)56000 +(14000 +16 )6 ) 654321 X 909090 +654321 X 909097)34 X 3535 35 X34348) 27000 + 1259)345345 + 1501510) 347 + 358 + 352 + 349C档（跨越导练）800 + 256000+ 1253600+8+558X 101 5874X 99150 X 40 + 5039600 + 255600 +

5、 ( 25 X 7)210 + 42 X 635X 68+68+68X 64成长足迹课后检测简便运算参考答案典题探究(1) 75 X 45 + 17 X 25=25X 3X45+17X25=25 ><135+17)=25 M52(2) 599996 + 49997 + 3998 + 407 + 89=600000+50000+4000 -4-3-2+407+89=65400+487=65887=25 >4X38=3800(3) (48 X 75 X 81) + ( 24X 25 X27)=48 登4 >75 及5 >81 及7=2不必=18(4) 137+4+25

6、=137+ ( 4X 25)=137+ 100=1.37将演练方阵（1）乘法交换律:A档ax b= bx a（巩固专练）乘法结合律：（axb） xc = ax （bxc）38 X 25X4 =38 X (25 X 4) =38X100 =380042 X 125X8 =42 X (125X8) =42X1000 =4200025 X 17X4=25X4X 17=100X17=1700(25X 125) X ( 8X4) =(25X4) X ( 125X 8)=100 X1000=10000049X4X 5=49 X (4X 5)=49 X 20=98038X 125X 8X 3(125X 25

7、) X45 X 289X2( 125X 12) X 8125X (12X 4)=(38 X3)X(125X 8) =125X (25X4)=289 X (5 X 2)=12 X (125X8)=125 X48=114X1000=125X 100=289X10=12X 1000=125X 8X 6=114000=12500=2890=12000=1000X 6=6000（2）乘法交换律和结合律的变化练习125X64=125X 8X 8=1000X 8=8000125X 88=125X 8X 11=1000X11=1100044X25=11 X (4X25)=11 X100=1100125 X 2

8、4=125X 8X 3=1000X 3=300025X 28=25X 4X 7= 100 X 7=700(3)加法交换律:357+288+143a+b=b+a158 + 395+ 105加法结合律：(a+b) +c = a+ (b+c)167+289 + 33129+235 + 171+ 165=357+ 143 + 288=500 + 288=788=158 + (395+ 105) =167+33+289=158+500=200+289=658=489=(129+ 171) + (235+165)=300 + 400=700r378+527 + 73169+ 78+2258+39+ 42+

9、61138 +293+62+ 107=378+ (527 +73) =169+ ( 78+ 22) = (58+42) + ( 39+61) = (138+62) + ( 293 + 107) =378 + 600=169 + 100=100 + 100=200 + 400=978=269=200=600(4)乘法分配律：(a+b) Xc=aXc+bXc正用练习(80 + 4) X 25(20+4) X 25(125+ 17) X 825 X (40+4)15X (20+ 3)=80X 25+ 4X 25 =20X 25 + 4X25 =125X 8+ 17X 8=25X 40+25X 4 =

10、15 X20+ 15X 38) 125 X ( 17 X 8) X 4=125X8X 4X 17=1000 48375 X 480 + 6250 X 48=480 X(375 + 625) =480000=2000+100=2100=500+100=600=1000+136=1136=1000+100=1100=300 + 45=345(5)乘法分配律正用的变化练习36X325 >4139X101125 >88201 X 24=(30+6) X 3=25 X ( 40+ 1)=39X ( 100+ 1)=125 X (80+8)=(200+1) X 24=30X 3+6X3=25X

11、40+25X1=39 X 100+39X 1=125 X 80+ 125X 8 =200 X 24+ 1 X 24=90+ 18=1000+25=3900+39=10000+ 1000=4800 + 24=108=1025=3939=11000=4824(6)乘法分配律反用的练习：34 X 72 + 34 X 28 35 X 37 + 65 X 3785X 82+ 85X 1825X 97 + 25X 376X 25+25X 24=34 X ( 72 + 28)=(35+65) X 37 =85 X ( 82+18)=25X ( 97+3)=(76+24) X 25=34X100=100X 3

12、7=85X100=25X100=100X25=3400=3700=8500=2500=2500(7)乘法分配律反用的变化练习:38X29+3875X 299+7564 X 199+6435X 68 + 68+68X 64=38 X 29+ 38 X 1=75 X 299+75 X 1=64X 199+64X 1=35X 68+68X 1 + 68X64=38 X ( 29 + 1)=75 X ( 299+ 1)=64 X ( 199 + 1)=68 X ( 35+ 1 + 64)=38X 30=75X 300=64X 200=68X100=1140=22500=12800=680013 X 9

13、9=13 X (100 1)=1300- 13=680009) 25 X 16 X125=25 X2X8X 125 =5000010) 75000 + 125 + 15=75 M 000 T 25 T 5=75 -15X1000 T25=5X8=12877900 +4+25=7900 寸4 25)=79=401)3)5)67 X 21 + 18 X 21 + 85 X=21 X(67+18)+85 79=21 X85+85 >79=85 N21+79)=8500222222 X 999999=222222 X (1000000- 1)=222222000000-222222=222221

14、777778 56000 +(14000 + 16)=56000 T4000 M6=4X 16=64B档79（提升精练）6）2) 321 X 81 + 321 X 19=321 >(81+19) =321004) 333333 X 333333 =111111* 999999 =111111X (1000000 1) =111111000000- 111111 =111110888889654321 X 909090 +654321 X 90909 =654321 >999999=654321 X (100000- 1)=654321000000 -654321=654320345

15、6797)9)34 X 3535 35 X 3434=34 X 35X 101 35X 34X 101=0345345 + 15015=345 X 1001 +(15 X 1001)=345 勺 5M001 T001=238) 27000 + 125=27 X 1000+ 125=27刈 =21610) 347 + 358 + 352 + 349 =350X4-3+8+2-1 =1400+6=1406C档（跨越导练）800 + 256000+ 1253600+8+5=(800X4) + ( 25X4)=(6000X 8) + ( 125X 8)=3600 + (8X 5)=3200+100=48000+ 1000=3600 + 40=32=48=9058 X 101 5858 X 101-58X 174 X 99=74X ( 1001)=58 X (101 1)=5