Answer :
Answer:
D. 5.5 miles
Explanation:
The time taken by both siblings = Half an hour = 0.5 hour
[tex]\text{Distance covered=Speed}\times Time[/tex]The brother walks away at a speed of 3.5 miles per hour. The distance covered by the brother in half an hour:
[tex]\begin{gathered} =3.5\times0.5 \\ =1.75\text{ miles} \end{gathered}[/tex]The sister runs at a speed of 7.5 miles per hour. The distance covered by the sister in half an hour:
[tex]\begin{gathered} =7.5\times0.5 \\ =3.75\text{ miles} \end{gathered}[/tex]Since they are moving in opposite directions, the distance between them will be the sum of the distances in each direction.
[tex]\begin{gathered} \text{Distance apart=1.75+3.75} \\ =5.5\text{ miles} \end{gathered}[/tex]The siblings are 5.5 miles apart after half an hour.