I am being observed by the head after half term. I teach bottom set year 3. I am in the process of teaching fractions of shapes and equivalent fractions. They are all doing really well and are understanding (lets just hope they don't forget it all over half term). I would now like to move onto fractions of amounts. The focus of the observation is mental maths throughout the lesson (which I am already slightly confused about). For the LA I was thinking of having a pizza base cut into halves or quarters. Using cut up tomatoes I would say 'what is half of 8?', they then share out 8 tomatoes between the pizza pieces. I would then like to extend the MA by saying find 3/4 of 8? But I feel this is not mental maths?? I am not sure. Getting in a muddle. Any ideas??