Given radius of each circle = 3cm.
If two circles touch each other externally, then the distance between their centres is equal to the sum of their radii.
AB = 3+3 = 6
AC = 3+3 = 6
BC = 3+3 = 6
Draw line segment AB = 6cm.
With A as centre and radius = 6 cm, mark an arc.
With B as centre and radius = 6 cm, mark an arc intersecting the previous drawn arc at C.
Join AC and BC.
Now, with A, B and C as centres and radius = 3 cm, draw three circles.
We can see that each circle will touch each other.