Problema Solution
Prella and Bodo travel at a rate of 6.5 kph for 0.25 hours until they reach the river's edge. the river is 100 meters wide. they op on their raft and cross the river at a rate of 2 kph. once on the other side of the river, they then spend 20 minutes passing through the sacred burial grounds at a rate of 2.5 kph and finally arrive at the castle. what was their average speed, in kph, for their journey back to the castle? express your answer as a decimal to the nearest tenth.
Answer provided by our tutors
the average speed v = total distance/total time
v = d/t
Prella and Bodo travel at a rate of 6.5 kph for 0.25 hours until they reach the river's edge:
t1 = 0.25 h
v1 = 6.5 kph
d1 = v1*t1 = 0.25*6.5 = 1.625 km
the river is 100 meters wide. they op on their raft and cross the river at a rate of 2 kph.
d2 = 100 = 0.1 km
v2 = 2 kph
t2 = d2/v2 = 0.1/2 = 0.05 h
once on the other side of the river, they then spend 20 minutes passing through the sacred burial grounds at a rate of 2.5 kph and finally arrive at the castle
t3 = 20 min = 20/60 = 1/3 h
v3 = 2.5 kph
d3 = v3*t3 = 2.5*(1/3) km
now we have
total distance traveled is
d = d1 + d2 + d3
d = 1.625 + 0.1 + 2.5*(1/3)
total time of the travel
t = t1 + t2 + t3
t = 0.25 + 0.05 +1/3
the average speed is
v = d/t
v = (1.625 + 0.1 + 2.5*(1/3) )/(0.25 + 0.05 +1/3)
v = 4.039 kph