I used this for an observation and got good feedback. I found my students could do the calculations for the different elasticities, how they found it hard to apply their knowledge. Print out a few copies of the work sheet and the pictures, students then have to decide what they are. I gave them all a piece of blue tack and they came up and put the goods on the board where they thought the good was inelastic PED, elastic PES etc. Once the students had done that they justified their decisions (evaluation) and completed the write up which is on the PowerPoint.