When a tap is turned halfway anti-clockwise, it makes a half turn, forming a straight angle of 180°. The handle points in the opposite direction from where it started.
Class 5 Mathematics Maths-Mela Chapter 3 Angles as Turns question answer
Class 5 NCERT Maths-Mela Chapter 3 Angles as Turns solution
Opening a tap halfway in the anti-clockwise direction means the handle has made a half turn. A half turn equals 180°, also called a straight angle. This angle looks like a straight line and shows the handle pointing in the opposite direction from the starting point. So, the angle formed by the halfway turn is a straight angle.
For more NCERT Solutions for Class 5 Mathematics Maths-mela Chapter 3: Angles as Turns Extra Questions & Answer:
https://www.tiwariacademy.com/ncert-solutions/class-5/maths/maths-mela-chapter-3/