Question

Richard is driving home to visit his parents. 150 mi of the trip are on the interstate highway where the speed limit is 65 mph . Normally Richard drives at the speed limit, but today he is running late and decides to take his chances by driving at 80 mph. How many minutes does he save?

Answer 1

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.

$t_1=\frac{x}{v_1}=\frac{150mi}{65mph}=2.30h\\\\t_2=\frac{x}{v_2}=\frac{150mi}{80mph}=1.875h$

Next, you calculate the difference between both times t1 and t2:

$\Delta t=t_1-t_2=2.30h-1.875h=0.425h$

This is the time that Richard saves when he drives with a speed of 80mph. Finally, you convert the result to minutes:

$0.425h*\frac{60min}{1h}=25.5min=25\ min\ \ 30 s$

hence, Richard saves 25.5 min (25 min and 30 s) when he drives with a speed of 80mph