Answer:
option A
Explanation:
given,
drive 4 km at 30 km/h and
another 4 km at 50 km/h
average speed for the whole 8 Km trip = ?
time for the trip of first 4 km
distance = speed x time
[tex]t_1 = \dfrac{d}{s}[/tex]
[tex]t_1 = \dfrac{4}{30}[/tex]
t₁= 0.1333 hr
time from another 4 km trip
[tex]t_2 = \dfrac{d}{s}[/tex]
[tex]t_2= \dfrac{4}{50}[/tex]
t₂ = 0.08 hr
average speed
[tex]s= \dfrac{d}{t}[/tex]
[tex]s= \dfrac{8}{0.1333 + 0.08}[/tex]
[tex]s= \dfrac{8}{0.2133}[/tex]
s = 37.50 Km/hr
Less than 40 Km/h
the correct answer is option A
