8.43×1/4+84.3×0.05+2.5×0.843=8.43x0.25+8.43x0.5+8.43x0.25=8.43x(0/25+0.5+0.25)=8.43x1=8.433.14平方+68.6×0.314=3.14平方+6.86x3.14=3.14x(3.14+6.86)=3.14x10=31.4