question_answer

A car moves for half of its total travel time with a speed 80 km/h and for next half of the time at 40 km/ h. The total distance covered is 60 km. Find the average speed of the car.

Answer:

Average speed of the car \[=\frac{\text{total}\,\text{distance}\,\,\text{travelled}}{\text{total}\,\,\text{time}\,\,\text{taken}}=\frac{{{S}_{1}}+{{S}_{2}}}{{{t}_{1}}+{{t}_{2}}}\] here \[S={{S}_{1}}+{{S}_{2}}\] \[60km=80\times \frac{t}{2}+40\times \frac{t}{2}\] \[\Rightarrow 60km=60t\,\,\Rightarrow t=1hr\] \[{{V}_{ave}}=\frac{s}{t}=\frac{60km}{1hr}=60km/hr\]