Construct a square, each of whose sides measures 6.4 cm.

All the sides of a square are equal.

Steps of construction:

Step 1: Draw $A B=6.4 \mathrm{~cm}$

Step 2: Make $\angle A=90^{\circ}$

$\angle B=90^{\circ}$

Step 3: Draw an arc of length 6.4 cm from point A and name that point as D.

Step 4: Draw an arc of length 6.4 cm from point B and name that point as C.

Step 5: Join C and D.

​Thus, ABCD is a required square.