54.9×0.38的简便方法解：采用分配律，原式=54.9x0.38=54.9x（0.4-0.02）=54.9x0.4-54.9x0.02=21.96-1.098=20.862
54.9x0.38=（55-0.1）x0.38=55x0.38-0.1x0.38=20.9-0.038=20.862
