Question

Tyler and Pearl went on a 20km bike ride that lasted for 3 hours. Because of steep hills or the trail, they walked for most of the trip. Their walking speed was 4km/hr. Their riding speed was 12km/hr. How much time did they spend walking?

Answer 1

Answer: 1 hour

Explanation:

Let the distance they walked be
`d_1` in time
`t_1` and the distance they walked be
`d_2` in time
`t_2` ,then

Walking speed=
`(d_1)/(t_1)=4`

`\\\Rightarrow\ d_1=4t_1`

Riding speed=
`(d_2)/(t_2)=12`

`\\\Rightarrow\ d_2=12t_1`

Also the total time taken=3 hours

∴
`t_1+t_2=3\\\Rightarrow\ t_2=3-t_1`...(1)

Since the total distance= 20 km

∴
`d_1+d_2=20\\\Rightarrow4t_1+12t_2=20\\\Rightarrow4t_1+12(3-t_1)=20..............[\text{from (1)}]\\\Rightarrow4t_1+36-12t_1=20\\\Rightarrow-8t_1=-8\\\Rightarrow\ t_1=1`

Thus, the they spent 1 hour time in walking.