Answer:272.711b km/h
Explanation:
Given
Average speed of car must be 257 km/h
and first half is covered by a speed of 243 km/h
and rest by, let say by v
average speed
[tex]V_{average}=\frac{total distance}{total time}[/tex]
[tex]257=\frac{1660}{t_1+t_2}[/tex]
Where [tex]t_1=\frac{830}{257}[/tex]
[tex]t_2=\frac{830}{v}[/tex]
[tex]257=\frac{1660}{\frac{830}{257}+\frac{830}{v}}[/tex]
[tex]\frac{1}{243}+\frac{1}{v}=\frac{2}{257}[/tex]
[tex]\frac{1}{v}=\frac{2}{257}-\frac{1}{243}[/tex]
v=272.711 km/h
