7.6*3.25+7.8*6.75
=7.6*3.25+（7.6+0.2）*6.75
=7.6*3.25+7.6*6.75+0.2*6.75
=7.6*(3.25+6.75)+0.2*6.75
=7.6*10+1.35
=76+1.35
=77.35
【观察得到3.25+6.75=10,可以利用其简便计算,于是将7.8拆成7.6+0.2】