△PQR has sides PQ=4cm, QR=6cm and RP=5cm. △ABC has sides AB=6cm, BC=9cm and CA=7.5cm.
(i) List the pairs of corresponding sides of the two triangles so that the sides are in the same order of magnitude.
(ii) Prove that the two triangles are similar.
(iii) Briefly explain why having the three pairs of corresponding sides in the same ratio is enough to claim that the two triangles are similar but not necessarily congruent.