Question

You are to drive to an interview in another town, at a distance of 270 km on an expressway. the interview is at 11:15

a.m. you plan to drive at around 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 45 km/h for 40 km. what would be the least speed needed for the rest of the trip to arrive in time for the interview?

Answer 1

Time needed for drive a distance 100 km at 100 km/h: t1 =100/100 = 1 h Time needed for drive a distance 40 km at 45 km/h: t2 =40/45 =0.8 h t3 =3h 15m - 1 h- 0.8 h =1.45 h Distance to town equals: s3 =270-100-40 =130 km Least speed needed to arrive in time for the interview: v3 =130 km/1.45 h =89.65 km/h The answer is 89.65 km/h