Let the functional relationship between y and s make y=ks,
K4=32,
The solution is k= 128,
The functional relationship between y and s is y =128s;
(2) When s = 2mm, y =1282 = 64m;
(3)∵y≤40,y= 128s,
∴ 128s≤40,
∴s≥3.2.
That is, if the total length of noodles does not exceed 40m, then the thinnest noodles should be 3.2mm2 。