← Thinking in Turns · Lesson 3 of 3
The order matters
In ordinary arithmetic, 2 + 3 is the same as 3 + 2. Cube moves are not like that: R then U leaves the cube differently from U then R. Mathematicians say the moves do not commute.
This is why cube methods are written as exact sequences, and why solvers work face by face, using sequences that change a few pieces and leave the rest alone.
Is "R then U" the same as "U then R" on a cube?
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