Question

How many right angles does an hour hand makes if it moves in a clockwise direction from 12 to 9?

• A. 2
• B. 3
• C. 1
• D. 4

Answer 1

The correct option is B 3

Consider the following clock showing the initial and final positions.
The angle formed between 12 and 9 is of $\frac{3}{4}$ of a complete angle.
Angle between them is $\frac{3}{4}$ x 360${}^{\circ }$= 270${}^{\circ }$
One right angle is equal to 90${}^{\circ }$.

So the number of right angles needed to reach 9 starting from 12 is = $\frac{{270}^{\circ }}{{90}^{\circ }}=3$

$\therefore$ Hence hour angle makes 3 right angles to reach 9 if it starts from 12 .