Steps of construction:
I.          Draw a line segment PQ = 5 cm.
II.         At P, draw  such that 
III.        From  cut-off PS = 4 cm.
IV.        With centre at 5 and radius = 5 cm, mark an arc towards Q.
V.          With centre Q and radius = 4 cm, mark an arc to intersect the previous arc at R.
VI.         Join RQ and Rs
              Thus, PQRS is the required rectangle.