1÷1.25×0.8不是简便计算。1÷1.25×0.8=0.8×0.8=0.64
1÷1.25×0.8=1×0.8÷1.25=0.8÷1.25=(0.8×0.8)÷(1.25×0.8)=0.64÷1=0.64