Answer:
20.25 minutes.
Explanation:
We have been given that Andres completed a 5-km race in 13.5 minutes. His sister’s time was 1 and 1/2 times longer than his time.
To find time taken by Andres's sister, we will multiply 13.5 by 1 and 1/2.
![\text{time taken by Andres's sister}=1(1)/(2)* 13.5\text{ min}](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ut2dwz7lztj0vrf5bt91urho8cwiev9i9m.png)
![\text{time taken by Andres's sister}=(3)/(2)* 13.5\text{ min}](https://img.qammunity.org/2020/formulas/mathematics/middle-school/4cdg6n8j0kqi6hrysff1lglbfuct8e7kks.png)
![\text{time taken by Andres's sister}=1.5* 13.5\text{ min}](https://img.qammunity.org/2020/formulas/mathematics/middle-school/cjcu1cj8c9ztih36en3zf2vdyqo1t6435h.png)
![\text{time taken by Andres's sister}=20.25\text{ min}](https://img.qammunity.org/2020/formulas/mathematics/middle-school/famvxyy1wvomgpu23ykk9s2mtens5e30kr.png)
Therefore, it will take Andres's sister 20.25 minutes to run the race.