加法、乘法运算律加法、乘法运算律： 加法交换律：a+b=b+a 加法结合律：a+b+c=a+(b+c) 乘法交换律：axb=bXa乘法结合律：axbxc=ax(bxc)乘法分配律：ax(b+c)=axb+axc 例1.计算：88x345+345x111。剑答疑编号0518350101] 【答案】68655 【解答】原式=345x(88+111) =345x199 =345x(200-1) =345x200-345x1 =69000-345 =68655 例2.计算：2008x1001—2005X999. &[答疑编号0518350102] 【答案】7013 【解答】原式=2008x(1000+1)—2005x(1000—1)=2008x1000+2008—2005x1000+2005 =(2008—2005)x1000+(2008+2005) =3000+4013 =7013 例3.计算：2005x20072007—2004x20082008. &[答疑编号0518350103] 【答案】30003 【解答】原式=2005x2007x10001—2004x2008x10001=(2005x2007—2004x2008)x10001 =[(2004+1)x2007—2004x2008]x10001=(2004x2007+2007—2004x2008)x10001=(2007—2004)x10001 =30003 例4.计算：99.9x77.7+33.3x66.6 G[答疑编号0518350104] 【答案】9980.01 【解答】原式=99.9x77.7+33.3x3x22.2 =99.9x77.7+99.9x22.2 =99.9x(77.7+22.2) =99.9x99.9 =99.9x(100—0.1)第1页 =99.9X100-99.9X0.1 =9990—9.99 =9980.01例5.计算：159X63+41X120—59X43. O[答疑编号0518350105] 【答案】12400 【解答】原式=(100+59)X63+(100—59)X120—59X43 =100X63+59X63+100X120—59X120—59X43 =100X63+100X120—59X(120+43—63) =100X63+100X120—59X100 =100X(63+120—59) =12400 例6.计算：73X62—27X38 O[答疑编号0518350106] 【答案】3500 【解答】原式=73X(100—38)—(100—73)X38 =73X100—73X38—100X38+73X38 =(73—38)X100 =3500 11x934--x234 例7.计算：：. O[答疑编号0518350107] 【答案】866 =11x934-(-+1)x234 【解答】原式 =HX934--X234-23477 =11x(934-234)-234 =11x700-234 7 =1100—234 =866 门丄灯5丄-111x17— 例8.计算：. 第2页 本文来源：https://www.wddqw.com/doc/0707709275a20029bd64783e0912a21614797f97.html