Calculate how much time could be saved if the train would run at its usual speed, given that it ran at 5/7 of its own speed and got to its destination in 15 hours?
Select:
A) 1.29 hrs
B) 2.29 hrs
C) 4.29 hrs
D) 5.29 hrs
E) 3.29 hrs

Rationale: "new speed = 5 / 7 of usual speed new time = 5 / 7 of usual time 5 / 7 of usual time = 15 hrs usual time = 15 * 5 / 7 = 10.71 hrs time saved = 15 - 10.71 = 4.29 hrs answer is c"
Answer: C