100 ml of 0.2 M hcl mixed with 100 ml of 0.2 m ch3cooh

Since your concentrations are only good to 1 significant figure, I think you can ignore the acidity of the acetic aicd - it just doesn't add a significant amount of protons.
So all it does is dilute the original HCl: 2M ---> 1M so the pH becomes 1.0.