To solve this problem, let us first assume that the bird was flying at zero acceralation (constant velocity) so that we can use the equations for linear motion. The formula relating velocity, distance and time is:
v = d / t
where
v = velocity = 45 km / hr
d = distance travelled = 1800 km
t = time elapsed = (unknown)
Rewriting in terms of t:
t = d / v
Substituting the given values to find for t:
t = 1800 km / (45 km / hr)
t = 40 hr
Therefore it takes about 40 hours for the bird to travel that distance.