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.