The mean is

(1 . \overset{\cdot}{2} + 2 . \overset{\cdot}{1}) / 2 = 3 . \overset{\cdot}{3} / 2 = 1 . \overset{\cdot}{6}

Alternatively, you can convert into fractions, to getthe answer of $1 \frac{2}{3}$ , which is the same as $1 . \overset{\cdot}{6}$ .