Answer:
54mph
Explanation:
Speed is defined as the change in distance of a body with respect to time.
Let x be the speed of Eric on his way to the football game, if he used 11hours to the football game, his distance will be the product of his speed and time taken i.e
Distance = speed × time
Distance= x × 11
Distance = 11x... (1)
During his return journey, his speed increases by 12mph with a return drive in only 9hours i.e speed = x+12 and time is 9hours
Since distance = speed × time (return Journey)
Distance = (x+12)×9
Distance = 9x+84...(2)
Note that the distance to and fro the journey is the same as such we will equate equations 1 and 2 to get his initial speed "x" to have;
11x = 9x+84
11x-9x = 84
2x = 84
x = 42mph
This means that his initial speed on his way to the football game is 42mph. Since his speed increases by 12mph during his return drive, his return speed will be 42mph + 12mph which gives 54mph.
