In the first half (distance) of a trip, a truck travels at a speed of 70 km/hr. How fast must it go during the second half of the trip to average 80 km/hr for the entire trip? km/hr

Respuesta :

so, there are 2 halves, now if the truck goes 90 mph on the second half, the average speed then will be 

[tex]\bf \cfrac{\stackrel{mph}{70}+\stackrel{mph}{90}}{\stackrel{half}{1}+\stackrel{half}{1}}\implies \cfrac{160}{2}\implies 80[/tex]