This is the boss. No calculator — the numbers are chosen to live in your head, and 0.606 rounds to six-tenths without shame. One long sound check, worked line by line, and every answer feeds the next: write them down as you go.

The whole chapter rides in it — the warmth in the speed of sound, $v = f\lambda$, the string's $\dfrac{v}{2L}$, and the beat that two close pitches make. 5★ under par here is the chapter crown. Tune the hall.