Question

A group of 7 campers has 4 hours to hike to a lighthouse and back before sundown. the lighthouse is 28 meters high. it is located 12 kilometers from camp. how fast do they have to walk?

Answer 1

Answer: So the campers must travel 12km two times (because they must go back after reached the lighthouse), and 28m two times.

If they keep the velocity constant (it means that they climb up and down the stairs at the same speed that they walk )

then you could add the whole distance as 12km*2 + 28m*2

a km is 1000m, so the distance will be 12000*2m+28*2m = 24046m

and they have 4 hours to do this, so the velocity is distance over time, they should do 24046m/4hours = 6011.5m/h or 6.0115km/h

Answer 2

We must take note that the 28 meters high is simply a diversion. What we only need is the 4 hours and 12 kilometers distance. The formula for calculating the speed or velocity is :

velocity = distance / time

Therefore:

velocity = 12 km / 4 h

velocity = 3 km / h = 0.83 m / s