A circular spinner is divided into 4 sections, as shown. The angles at the centre of the circle in the sections labelled Green and Blue each measure $90^{\circ}$. An arrow is attached to the centre of the spinner. The arrow is spun once. What is the probability that the arrow lands on either Red or Yellow?
(A) $\frac{1}{8}$
(D) $\frac{1}{2}$
(B) $\frac{1}{4}$
(E) $\frac{3}{4}$

![](https://cdn.mathpix.com/cropped/2024_04_20_6ed09463f225f8ba1f07g-009.jpg?height=349&width=341&top_left_y=259&top_left_x=1312)
The total central angle in a circle is $360^{\circ}$.

Since the Green section has an angle at the centre of the circle of $90^{\circ}$, this section corresponds to $\frac{90^{\circ}}{360^{\circ}}=\frac{1}{4}$ of the circle.

This means that when the spinner is spun once, the probability that it lands on the Green section is $\frac{1}{4}$.

Similarily, the probability that the spinner lands on Blue is also $\frac{1}{4}$.

Since the spinner lands on one of the four colours, the probability that the spinner lands on either Red or Yellow is $1-\frac{1}{4}-\frac{1}{4}=\frac{1}{2}$.

ANSWER: (D)