五年级简便运算(1).docx

1、五年级简便运算(上册)(朵朵)回忆四那么运算定律，并举例说明加法交换律加法交换律a+b=b+a例：74-8=8+7加法结合律乘法交换律乘法结合律乘法分配律(a+b)+c=a+b+c)ab=baabc=a(bc)例：(20+55)+45=20+(55+45)例：5X6=6X5例：(6X25)X4=6X(25X4)乘法分配律的逆运算a+b)c=ac+bc例：25+125)X8=25X8+125X8ac+bc=(a+b)c例：25X55+25X45=25X55+45)i第一种：连乘一乘法交换律的应用例题：5X4.3X204.5X3X2涉及定律：乘法交换律ahc=ac-h1第二种：乘法分配律的应用例题

2、：(10+0.1)x27(0.5+5)x4(5+0.2)xl6涉及定律：乘法分配律(a±b)xc=ac±bei第三种：乘法分配律的逆运算例题：0.5x3.2+4.8X0.520x0.58+0.58x800.8x7+0.2x7涉及定律：乘法分配律逆向定律axb±axc=a(b±c)i第四种：添加因数“1”例题：4.5-4.5x0.20.8x6-0.81.8x23+2.2x23+23涉及定律：乘法分配律逆向运算“1，将其中一个数转化为IX"的形式，将原式转化为两两之积相加减的形式，再提取公有因数，按乘法分配律逆向定律运算。练习10.1X6.40.8

3、X35.4X12.52.5XX2.53.45X9.8+3.45X0.24x127+4x29+57x4567+98213x12.5x67x8127-56-165.83-2.97-1.2198.76-4.5-0.26-5.5-1.7471.3-(61.3-23.7)6.72-(4.68-1.28)124.68+324.68+524.68+724.68+924.682.5X15.7X412.5X4.6X82.5X32X0.125456X7894-1234-456X1234-7897.9X10.15.8X9.999X564,5X10.27.8X0.9920.3X670.77X46+7.7X5.40.7

4、7X46+7.7X5.412.5X34+25X3318X222.2-666.63.6X31.4+43.9X6.495.67-3.5-0.78-6.5-3.2245.8X10.169.7+(48.4-19.7)0.888X12.X0.9+0.015795.5795+5.975X579.515.7X24+1.57X7602.8+29+7.2+2197.8-17.8+4.9)125X1.6X4.830.2X4656X0.9967.2X40-60.2X408.4X29-18X8.48.48.4X29-18X8.48.46.4X1235.6X64+330X0.6415.6X13.1-15.6-15.6X2.14.8X7.8+78X0.520.25X16.2X4(1.250.125)X83.6X1023204-1.254-83.72X3.5+6.28X3.54.8X7.8+78X0.520.8X100.118.76X9.9+18.763.52+2.54-0.456.5X9.9+56.518.76X9.9+18.763.524-2.54-0.43204-1.25+80.79X1990.32X4032.4X1020.85X199(2.5-0.25)X0.4(1+0.1)+(2+0.1X