Answers

  • Brainly User
2015-09-04T23:56:28+08:00
DISTANCE (D) = RATE (R) × TIME (T)

D =  R × T                 T = D/R         R = D/T

DOWNHILL:
    Distance               Rate               Time
      80 km            40 km/hr                80 km ÷40 km/hr = 2 hr

UPHILL (going back)
    Distance               Rate                Time
       80 km            10 km/hr              80 km ÷ 10 km/hr = 8 hr

TO GET AVERAGE SPEED:
     Total Distance ÷ Total hours = Average Speed    (R = D/T)
       (80 km + 80 km) ÷ (2 hr + 8 hr)  = Average Speed
               160 km   ÷  10 hr  =  16 km/hr    or  16kph

John's average distance is 16 kph.
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