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 \[S={{S}_{1}}+{{S}_{2}}\]
\[60km=80\times \frac{t}{2}+40\times \frac{t}{2}\]
\[\Rightarrow 60km=60t\,\,\Rightarrow t=1hr\]
\[{{V}_{ave}}=\frac{s}{t}=\frac{60km}{1hr}=60km/hr\]
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