Question

A car travels the first 50 km of its journey at an average speed of 25 m/s and the next 120 km at an average speed of 80 km/h. The car completes the last part of its journey at an average speed of 90 km/h in 35 minutes. Find the average speed for its entire journey, giving your answer in km/h.​

Answer 1

Answer:81.85 km/hr is the average speed

Explanation:

Answer 2

Answer: ≈ 84,3 km/h.

Explanation:

`\displaystyle\\V{average}=(\Delta S)/(\Delta t)=(S_1+S_2+S_3)/(t_1+t_1+t_3) .\\1.\ S_1=50\ km\\ t_1=(S_1)/(V_1)\\ V_1=25*(3600)/(1000) \\V_1=90\ (km)/(h) .\\t_1=(50)/(90)\\ t_1=(5)/(9) \ h.\\2.\ S_2=120\ km\ \ \ \ V_2=80\ (km)/(h) \\t_2=(S_2)/(V_2) \\t_2=(120)/(80) \\t_2=(3)/(2)\ h.\\`

`3.\ V_3=90\ (km)/(h) \\t_3=35\ minutes\\t_3=(35)/(60) \\t_3=(7)/(12)\ h.\\ S_3=V_3*t_3\\S_3=90*(7)/(12) \\S_3=52,5\ km.\\Hence,\\V{average}=(50+120+52,5)/((5)/(9)+(3)/(2) +(7)/(12) ) \\V{average}=(222,5)/((95)/(36) ) \\Vaverege\approx84,3\ (km)/(h) .`