Problema Solution
If a cyclist had gone 3km/hr faster id would have taken 1 hour 20 minutes less to ride 80km. What time did he take?
Answer provided by our tutors
let
v = the speed of the cyclist
t = the time of the cyclist
d = 80 km
v*t = d
v*t = 80 => v = 80/t
if a cyclist had home 3km/hr faster he would have taken 1 hour and 20 minutes less to ride 80km.
1 hour 20 min = 1 + 20/60 = 4/3 hr
(v + 3)*(t - 4/3) = 80
plug v = 80/t into the last equation
(80/t + 3)*(t - 4/3) = 80
by solving the equation we find and consider the positive roots only since t>0
t = 20/3 h = 6 h 2*60/3 min = 6h 40 min
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it took him 6 hours and 40 minutes to pass the 80 km.