人大附中華杯賽資料加法乘法運(yùn)算律

1、實(shí)用文檔用心整理10千里之行始于足下加法、乘法運(yùn)算律加法、乘法運(yùn)算律:加法交換律:a + b = b+ a加法結(jié)合律:a + b + c= a+( b + c)乘法交換律:ax b= bXa乘法結(jié)合律:ax bx c= ax( bx c)乘法分配律:ax( b + c) = ax b+ axe例1.計(jì)算:88 x 345+ 345 x 111。答疑編號(hào) 0518350101【答案】68655【解答】原式=345x( 88+ 111) =345x 199 =345x( 200-1 ) =345x 200-345x1 =69000 - 345 =68655例 2.計(jì)算：2008x 1001 200

2、5x 999.答疑編號(hào) 0518350102【答案】70131000 1)【解答】原式=2008X( 1000 + 1) 2005X( =2008X 1000+ 2008 2005X 1000+ 2005 =(2008 2005)X 1000+( 2008 + 2005)=3000+4013 =7013例 3.計(jì)算：2005X 20072007 2004X 20082008.答疑編號(hào) 0518350103【答案】30003【解答】原式=2005X 2007X 10001 - 2004X 2008X 10001=(2005X 2007- 2004X 2008)X 10001=(2004 + 1)

3、X 2007- 2004X 2008 X 10001=(2004X 2007+ 2007 2004X 2008)X 10001=(20072004)X 10001=30003例 4.計(jì)算：99.9 X 77.7 + 33.3 X 66.6答疑編號(hào) 0518350104【答案】9980.01【解答】原式=99.9 X 77.7 + 33.3 X 3X 22.2=99.9 X 77.7 + 99.9 X 22.2=99.9 X( 77.7 + 22.2 )=99.9 X 99.9=99.9 X( 100 0.1 )=99.9 X 100 99.9 X 0.1=9990 9.99=9980.01例

4、5.計(jì)算：159X 63+ 41 X 120 59X 43.答疑編號(hào) 0518350105【答案】12400【解答】原式=(100 + 59)X 63+( 100 59)X 120- 59X 43 =100X 63+ 59X 63+ 100X 120 59X 120 59X 43 =100X 63+ 100X 120 59X( 120 + 43 63) =100X 63+ 100X 120 59X 100 =100X( 63+ 120 59)=12400例 6.計(jì)算：73X 62 27X 38答疑編號(hào) 0518350106【答案】3500【解答】原式=73X( 100-38)-( 100 73)X 38 =73 X 100-73 X 38 - 100 X 38 + 73 X 38 =(73- 38)X 100=3500例7.計(jì)算:答疑編號(hào) 0518350107【答案】866