Question

Julia rides her horse 18 km with a constant speed of 6km/hr and another 24 km with a constant speed of 12 km/hr. What is her average speed for the total trip? PLZ HELP!

Answer 1

8.4 km/hr.

Explanation:

We have been given that Julia rides her horse 18 km with a constant speed of 6 km/hr.

Let us find the time taken by Julia to cover a distance of 18 km.

`\text{Time}=\frac{\text{Distance}}{\text{Speed}}`

`\text{Time taken to cover 18 km}=\frac{18\text{ km}}{\frac{6\text{km}}{\text{hour}}}`

`\text{Time taken to cover 18 km}=\frac{18\text{ km}}{6}*\frac{\text{hour}}{\text{km}}`

`\text{Time taken to cover 18 km}=(18)/(6)*\text{hour}`

`\text{Time taken to cover 18 km}=3\text{ hour}`

We are also told that she rides another 24 km with a constant speed of 12 km/hr.

Let us find the time taken by Julia to cover a distance of 24 km.

`\text{Time taken to cover 24 km}=\frac{24\text{ km}}{\frac{12\text{km}}{\text{hour}}}`

`\text{Time taken to cover 24 km}=\frac{24\text{ km}}{12}*\frac{\text{hour}}{\text{km}}`

`\text{Time taken to cover 24 km}=(24)/(12)*\text{hour}`

`\text{Time taken to cover 24 km}=2\text{ hour}`

Since we know that
`\text{Average speed}=\frac{\text{Total distance}}{\text{Total time}}`.

Upon substituting our values in above formula we will get,

`\text{Julia's average speed}=\frac{18\text{ km}+24\text{ km}+}{3\text{ hour}+2\text{ hour}}`

`\text{Julia's average speed}=\frac{42\text{ km}}{5\text{ hour}}`

`\text{Julia's average speed}=\frac{8.4\text{ km}}{\text{ hour}}`

Therefore, Julia's average speed is 8.4 km per hour.