Respostas

2013-08-13T19:01:44-03:00
T (inicial) = 8 h
S (inicial) = 100 km

T (final) = 12 h
S (final) = 400 km

Delta S = S(inicial) - S(final) :
300 km
Delta T = T(inicial) - T(final) :
4 h

300 km em 4 h 
300 / 4 = 75 km / h
1 5 1