distance is velocity times time
d = vt
when riding tricycle:
d = 5t ---equation 1
(5kph is the velocity, t is the time)
when walking
d = 4 (t + 0.5) ----equation 2
(4 is the velocity, 't+0.5' is the time')
equating equation 1 and 2
5t = 4(t+0.5)
5t = 4t + 2
5t - 4t = 2
t = 2hours
substitute t=2 to equation 1
d = 5kph(2hours)
d = 10km
