Answer:
The expression for Leah’s total travel time is 20r+150 r(r+15)Step-by-step explanation:
We know, time = distance/speed
Distance= 10 mi
Speed of car = r mi/h
Time taken by car = 10/r h
Speed of commuter rail = r+15 mi/h
Time taken by rail = 10/(r+15)
Total time for the trip:
10/r +10/r+15
= 10(r+15)/r(r+15) + 10r/r(r+15)
=10r + 150 + 10r/r(r+15)
= 20r +150/r(r+15).....(1)
At a driving rate of 30 mph, putting r = 30 in equation (1) total time,
20r+150/r(r+15) = 20(30)+150/30(30+15)
= 750/1350
= 5/9 h
= 5/9×60
= 33.33 min
= 33 min ( by rounding off)
The expression for Leah’s total travel time is 20r+150 r(r+15)
The total time is 5/9 h, or about 33 min