Then, MS is
the shadow of the man Let MS = s metres Note that
∆MSN ~ ∆ASB
or
MS
AS  = MN
AB
or
AS = 3s (as MN =
2 and AB = 6 (given))
Thus
AM = 3s – s = 2s But AM = l
So
l = 2s
Therefore
dl
dt  = 2 ds
dt
Since 
5
dl
dt =
km/h