1240*3.4+1.24*2300+12.4*430
=1240*3.4+1.24*1000*2.3+12.4*100*4.3
=1240*3.4+1240*2.3+1240*4.3
=1240*(3.4+2.3+4.3)
=1240*10
=12400
1240*3.4+1.24*2300+12.4*430简便计算
1240*3.4+1.24*2300+12.4*430
=1240*3.4+1.24*1000*2.3+12.4*100*4.3
=1240*3.4+1240*2.3+1240*4.3
=1240*(3.4+2.3+4.3)
=1240*10
=12400