This is the boss. No calculator, and one lifting bracket taken the whole way: the load per millimetre of weld, the throat that load demands, the leg size the print calls up, the heat input of the pass, the drill speed for the bolt holes, and the wrench setting that closes the job out. Every answer feeds the next — write each line down as you go, because one early slip rolls all the way to the torque wrench.

Two roundings are announced, and they are the shop's own, not a shortcut. $\sqrt{2}$ is taken as 1.4, so a throat becomes a leg by multiplying by 1.4 instead of 1.4142 — you are rounding UP to a stocked gauge afterwards anyway, and the difference never survives that. And the spindle-speed relation is used in its wall-chart form, $N = \dfrac{320\,V}{d}$, which is the exact $N = \dfrac{1000\,V}{\pi d}$ with $1000/\pi = 318.3$ rounded to 320 for mental work. Every other figure on this bracket is exact.

Note what the third line actually asks. It does not want another number; it wants a DECISION — which gauge in the rack goes on the print — and weld sizing rounds UP, never to the nearest. The arithmetic is only there to earn you the right to make that call.

Everything in the chapter rides in this one bracket. 5★ under par here is the chapter crown. Clock in.