Alex drives to and from work each day along the same route. If he driv

Since Alex drives to and from work along the same route, the distance he travels is same in both the onward and return journeys. As mentioned in the question, this is a round trip.

When the distance is same for the onward and return journeys (i.e. in round trips),

Average Speed = \(\frac{2*a*b }{ a + b}\),

where, a = speed for onward journey and b = speed for return journey

In Alex’s case, speed for onward journey = 80 miles per hour and speed for return journey = 100 miles per hour

Therefore, average speed of Alex for the round trip = \(\frac{2 * 80 * 100 }{ 180}\) = \(\frac{16000 }{ 180}\) = \(\frac{1600 }{ 18}\).

Note that 18 * 9 = 162, therefore, 18 * 90 = 1620. Since the numerator is 1600, the result should be slightly less than 90; there is one obvious choice in that case and that is 88.9

The correct answer option is B.