This is the fifth section of Chapter 5: Measurement of Circles. We developed the formula for the area of circles by cutting a circle up into equal sectors, and arranging the sectors to form a shape that was very close to a parallelogram (link to animation of this proof, along with mathematical thinking).
The students decided that the following exercises were the most important: p. 166, #4, 5, 6, 8, 10, 14, 15 and 16. We will be checking that problems have all been attempted by Friday. It isn't necessary to have completed all the problems, or even to get the right answer. However, in order to get full marks for classwork, every problem must have at least been tried.