A motorcyclist travels for 15 minutes at 120km/h, 1h 30mins at 90km/h and 15 minutes at 60km/h. At what speed would she have to travel to perform the same journey, in the same time, without changing speed?

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Answer 1 · 2018-03-19T09:16:41

#90"km/h"#

The total time taken for the motorcyclist's journey is

#0.25"h" (15"min") + 1.5"h" (1"h" 30"mins") + 0.25"h" (15"min") = 2 "hours"#

The total distance travelled is

#0.25\times120 + 1.5\times90 + 0.25\times60 = 180"km"#

Therefore the speed she would have to travel at is:
#180/2 = 90"km/h"#

Hope that makes sense!