Question 1038021
Speed is x mph, and in 3 hours, he went 3x miles.  In the last hour he went (1/5)x miles
He drove 3x+(x/5) =512 km
(16/5)x=512
x=512*5/16=160 km/h  ANSWER
In 3 hours he made 480 km.  The last hour he drove 1/5 of that speed, or 32 km.