Step 1 : Draw a line segment AB = 6 cm.
Step 2 : Construct ∠ ABX = 90o.
Step 3 : With B as the centre and radius 5 cm, draw an arc cutting ray BX at Y.
Step 4 : Draw line PQ parallel to AB through point Y.
Step 5 : With B as centre and radius equal to 4.2 cm, draw an arc to cut line PQ at C.
Step 6 : With C as centre and radius equal to 6 cm, draw an arc to cut line PQ at point D.
Step 7 : Join points A, D and points B, C.
ABCD is the required parallelogram.