If you add 25ml chemical to 50ml H2O, pour out 25ml of the solution, then another 25ml of the chemical, what's the ratio of chemical to H2O?

After mixing 25 ml chemical to 50 ml H₂O, in the mixture :
Volume of chemical = 25 ml
Volume of water = 50 ml

After 25 ml of the above solution is poured out, 50 ml solution is left. In the solution :
Volume of chemical = (25 ml) × (50/75) = 50/3 mL
Volume of water = (50 ml) × (50/75) = 100/3 mL

After another 25 ml of the chemical is added, in the solution :
Volume of chemical = [(50/3) + 25] mL = 125/3 mL
Volume of water (unchanged) = 100/3 mL

Ratio of chemical : H₂O = (125/3) : (100/3) = 5 : 4