2 WHOLE LESSONS: Interior angle sum of triangle

This is really two lessons in one. I use it over two successive lessons. The first lesson covers basic angle sum of a triangle and the second the special case of the isosceles triangle. The starter gets students to estimate 10 angles and then the powerpoint takes students through how to calculate the missing angle in a diagram. The resource contains two booklets that can be printed off in booklet form for the students to write on....thus no time wasted drawing diagrams. The numbers are normally multiples of 5 and so this can be done mentally