Question

What fraction of a straight angle is a right angle?
A. $\dfrac{1}{4}$
B. $\dfrac{1}{2}$
C. $\dfrac{1}{8}$
D. None of these.

Answer 1

Hint: To solve this question, we should know the concept of fraction. Fraction can be defined as the ratio of the number of parts we have to find to the total number of parts in a whole. Mathematically, we can write it as, $\text{Fraction=}\dfrac{\text{Number of parts}}{\text{Total number of parts}}$.

Complete step by step answer:
In this question, we are asked to find what fraction of a straight angle is a right angle. We know that a straight angle is the angle which changes the direction of a line to the opposite direction, that is, in terms of degree, it is equal to ${{180}^{\circ }}$. Also, we know that the right angle is nothing but ${{90}^{\circ }}$. So, to find the fraction of right angle to straight angle, that is, ${{90}^{\circ }}$ to ${{180}^{\circ }}$, we need to know the concept of fraction.
Fraction is the ratio of the number of parts we have to find to the total number of parts. Mathematically, we can write it as, $\text{Fraction=}\dfrac{\text{Number of parts}}{\text{Total number of parts}}$.
Fraction of ${{90}^{\circ }}$ to ${{180}^{\circ }}$ is, $F=\dfrac{{{90}^{\circ }}}{{{180}^{\circ }}}\Rightarrow \dfrac{1}{2}$.
Therefore, we get the fraction of ${{90}^{\circ }}$ to ${{180}^{\circ }}$ as $\dfrac{1}{2}$.
Therefore, option (B) is the correct answer.

Note: In this question, the students might get confused with what a straight angle is. So, the students must note that a straight angle is basically the angle which changes the direction of a line to the opposite direction. If we draw a line, the straight angle that we would get would be ${{180}^{\circ }}$.