原式＝7.2×（1÷4）+2.8÷4＝7.2×1÷4+2.8÷4＝7.2÷4+2.8÷4＝（7.2+2.8）÷4＝10÷4＝2.5
7.2×0.25+2.8÷4=7.2×0.25+2.8×0.25=(7.2+2.8)×0.25=10×0.25=2.5
