60° 70° 80° 90° 100° 110° 120° Angles recap Here are some angles. [GM1.1 Core Starter] Here are some angles. 20° 30° 40° 50° 60° 70° 80° 90° 100° 110° 120° Which of the angles could: a) fit together to make a straight line? b) be vertices of the same triangle? c) fit together round a point? Preamble A straightforward investigation involving pupils, as individuals or in pairs, working systematically. Possible content Sum of angles in a triangle, straight line and round a point. Working systematically. Elements of non-calculator additions. Resources None. Solution/Notes a) (all in degrees) 20, 30, 40, 90 20, 30, 50, 80 20, 30, 60, 70 30, 40, 50, 60 30, 40, 110 30, 50, 100 40, 60, 80, 100, 80 110, 70 120, 60etc. b) (all in degrees) 120, 40, 20 110, 20, 50 100, 30, 50 , 20, 60 90, 40, 50 90, 20, 70 90, 30, 60 80, 70, 30 80, 60, 40 70, 60, 50 etc. c) (all in degrees) , 110, 100, 30 20, 40, 60, 110, 100, 30 120, 100, 50, 40, 20, 30 120, 90, 60, 50, 40, etc. Original Material © Cambridge University Press 2010 Original Material © Cambridge University Press 2010