I don't understand the problem

Question

A 75.0 mL portion of a 1.50 M solution is diluted to a total volume of 228 mL. A 114 mL portion of that solution is diluted by adding 189 mL of water. What is the final concentration? Assume the volumes are additive.

Answer 1

Molarity is defined as (moles of solute)/(liters of solution) so 1.50M means 1.50 moles/liter.

Turn the 75.0 mL into liters by dividing by 1000 so 75 mL = 0.0750 L

Multiply 0.0750 L by 1.50 moles/Liter and you find that the solution contains 0.1125 moles of solute. Now dilute it so the total volume is 228 mL or 0,228 L. The 0.1125 moles of solute is still there so it now has a molarity of (0.1125 moles)/(0.228 L) = 0.49342 M.

Now take out 114 mL or 0.114 L. How many moles of solute are in it? (0.49342 moles/L)(0.114 L) = 0.05625 moles.

Now add 189 mL of water. That makes the total amount of volume 114 + 189 = 303 mL or 0.303 L. Note that the 0.05625 moles of solute are still there as well.

That makes the final concentration (0.05625 moles.)/(0.303 L) = 0.186 M