Agroup 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?

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

the answer is b ) square root of 5

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it