Given:
Average Speed of the whole jouney is 60 km/hr
At first he travelled at an average speed of 70 km/hr
Average speed of remaining journey be x km/hr
[tex]\begin{gathered} 60=\frac{70+x}{2} \\ 60\times2=70+x \\ 120=70+x \\ x=120-70 \\ x=50\text{ km/hr} \end{gathered}[/tex]Therefore, average speed of remaining journey be 50 km/hr