The speed is 45/1, or just 45, and the time is 2.5h. The formula for distance is speed x time.
45 x 2.5
The easiest way to do this quickly using mental math is to break up the non-whole term and multiply its parts.
45 + 45 + (45/2)
45 + 45 + 22.5
90 + 22.5
112.5