Construct a square of side 3 cm.

Steps of Construction:

(i) Draw a line segment AB = 3 cm.

(ii) Construct 90° at A and B.

(iii) With A as centre and radius = 3 cm, mark an arc which intersects the ray through A in D.

(iv)With B as centre and radius = 3 cm, mark an arc which intersects the ray through B in C.

(v) Join CD.

Thus, the required square is ABCD.