Verified answer

[tex]t = \frac{d_{1}}{v_{1}} + \frac{d_{2}}{v_{2}} \\ \\ = \frac{20}{20} + \frac{40}{50} \\ \\ = \frac{100 + 80}{100} \\ \\ = \frac{180}{100} \\ \\ = 1.8[/tex]

[tex]average \: = \frac{ d_{1} +d_{2} }{t} \\ \\ = \frac{20 + 40}{1.8} \\ \\ = \frac{60}{1.8} \\ \\ = 33.333[/tex]

Explanation:

speed of the entire journey is 50km/hr. 20+40=60 km. km/hr. Thus, the answer is 200/hr.