Question

You drive 4 km at 30 km/h and then another 4 km at 50 km/h. What is your average speed for the whole 8-km trip?

Answer 1

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

$t_1 = \dfrac{d}{s}$

$t_1 = \dfrac{4}{30}$

     t₁= 0.1333 hr

time from another 4 km trip

$t_2 = \dfrac{d}{s}$

$t_2= \dfrac{4}{50}$

     t₂ = 0.08 hr

average speed

     $s= \dfrac{d}{t}$  

     $s= \dfrac{8}{0.1333 + 0.08}$  

     $s= \dfrac{8}{0.2133}$  

            s = 37.50 Km/hr

Less than 40 Km/h

the correct answer is option A