Angles as turns

In your book, Maths Mela (Chapter 3), Pragya joins a green straw and a yellow straw at their ends with paper clips. She holds the green straw steady and turns the yellow straw around the joint. As the yellow straw turns, the two straws make an angle. Angles come from turns!

When the yellow straw makes a quarter (1/4) of a full turn, the two straws look like the corner of a page: that is a right angle. When it turns LESS than a quarter turn, the straws make a narrow, pointed angle: an acute angle. When it turns MORE than a quarter turn but LESS than a half turn, the angle is wide open: an obtuse angle.

When the yellow straw makes two quarter turns, which is a half turn, the two straws lie in one straight line. This is called a straight angle. The book also shows a paper fan opened with one side kept fixed: a little way open is acute, opened a quarter turn is a right angle, a bit wider is obtuse, a half turn is a straight angle, and opened all the way round is a full turn.

The yellow straw can go on turning. Three quarter turns make a 3/4 turn, which is more than a straight angle. Four quarter turns make a full turn, and the yellow straw is back on top of the green one, where it started.