Answer:
t = 25.5 min
Explanation:
To know how many minutes does Richard save, you first calculate the time that Richard takes with both velocities v1 = 65mph and v2 = 80mph.
Next, you calculate the difference between both times t1 and t2:
This is the time that Richard saves when he drives with a speed of 80mph. Finally, you convert the result to minutes:
hence, Richard saves 25.5 min (25 min and 30 s) when he drives with a speed of 80mph