For the silicon chip the area is A=1 cm² and for the transistors the area is At=L² (L=linear size) . Then since N= 10 billion transistors of area At should fit in the area A
A=N*At
A=N*L²
solving for L
L= √(A/N)
Assuming that 1 billion=10⁹ (short scale version of billion), then