Is it possible to reduce the amount of cement and water by adding a water-reducing agent to concrete?

everyone knows that water-reducing agents have the effect of reducing water, so for example, the mix ratio i calculated is: cement 300: sand: 160: gravel: 1000: water 120: water reducing agent: %1.5. if the water reducing rate of the water reducing agent is 20%, then my mix ratio should not be: cement 300: sand: 160:…