a What sizes of angle (from 0 to 360) can it be used to measure? Angles GM3.2 Extension Starter Here is a circular protractor which has been cut into pieces like a puzzle. a What sizes of angle (from 0 to 360) can it be used to measure? b The circular protractor has five pieces. Can you find a way to measure the same angles, but using only four pieces? Preamble This is a short investigation based on a circular protractor. Pupils tend to forget about angles greater than 180, so they might need nudging in this direction. Possible content Mental arithmetic, trial and improvement. Resources None. Solution/Notes These angles may be measured: 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270°, 300° and 330°. Two ways to measure the same angles by splitting the protractor into four pieces are shown below.