NaOH%=m(NaOH)/m总 *100%=(40g*10%+60g*20%)/(40g+60g) *100%=16%
(40g×10%+60g*20%)/(40+60)=16%
(40*0.1+60*0.2)/(40+60)*100%=1.6%
a%=(40*10%+60*20%)/(40+60)=16%