You are to drive to an interview in another town, at a distance of 310 km on an expressway. The interview is at 11:15 a. m. You plan to drive at 100 km/h, so you leave at 8:00 a. m. to allow some extra time. You drive at that speed for the first 100 km, but then construction work forces you to slow to 42.0 km/h for 42.0 km. What would be the least speed needed for the rest of the trip to arrive in time for the interview

Question

Deanna Frank

Physics

1 July, 17:57

You are to drive to an interview in another town, at a distance of 310 km on an expressway. The interview is at 11:15 a. m. You plan to drive at 100 km/h, so you leave at 8:00 a. m. to allow some extra time. You drive at that speed for the first 100 km, but then construction work forces you to slow to 42.0 km/h for 42.0 km. What would be the least speed needed for the rest of the trip to arrive in time for the interview

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Answers (1)

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Carissa Malone · Answer 1

Time to cover first 100 km = 1 hour.

time remaining = 3.15 - 1 = 2.15 hour.

Time to cover next 42 km = 1 hour.

Time remaining = 2.15-1 = 1.15 hour.

Distance to be covered = 310 - 142

= 168 km

least speed needed = distance remaining / time remaining

= 168 / 1.15

= 146.08 km / h.