25.25÷2.5+7.5×0.4(巧算)拜托了各位 谢谢

问题描述:

25.25÷2.5+7.5×0.4(巧算)拜托了各位 谢谢

25.25÷2.5+7.5×0.4 =(25+0.25)÷2.5+(5+2.5)×0.4 =25÷2.5+0.25÷0.5+5×0.4+2.5×0.4 =10+0.1+2+1 =13.1