Prove that you can make any type of logic gate using just NAND gates.

In an extension to the Stonehenge problem, consider the mechanical possibilities for an arrangement of frictional rollers.

This is the technology section of stemNRICH - Core.

PhysNRICH is the area of the StemNRICH site devoted to the mathematics underlying the study of physics

This is the area of the advanced stemNRICH site devoted to the core applied mathematics underlying the sciences.

An introduction to a useful tool to check the validity of an equation.

Estimate these curious quantities sufficiently accurately that you can rank them in order of size