9×55+49 128×8 302×25 用简便方法计算过程.

9×55+49 =9×（49+6）+49 =9×49+9×6+49 =9×49+49+54 =（9+1）×49+54 =490+54 =544 128×8 =(125+3)×8 =125×8+3×8 =1000+24 =1024 302×25 =（300+2）×25 =300×25+2×25 =7500+50 =7550