Va rog rapid!dau coroana

Lungimea unei zale
L za = 2 cm = 20 mm
Grosimea unei zale = grosimea sarmei din care este confectionat:
G = 4 mm
Daca avem doar 2 zale, lungimea este de 2 × 20 mm din care scadem pierderile la inbinare (4 mm + 4 mm).
⇒ L_lant de 2 zale = 2 × 20 - (4 + 4) = 2 × 20 - 2 × 4 = 40 - 8 = 32 mm
La 3 zale avem 2 imbinari.
La 4 zale avem 3 imbinari.
La 5 zale avem 4 imbinari.
................................................
La n zale avem (n-1) imbinari si la o imbinare se pierd 2 grosimi de za.
.
[tex]\displaystyle\bf\\Rezolvare:\\\\1~m=1000~mm\\n\times20 - (n-1)\times (4+4)\geq 1000\\\\20n-8(n-1)\geq 1000\\\\20n-8n+8\geq 1000\\\\12n+8\geq 1000\\\\12n\geq1000-8\\\\12n\geq992\\\\n\geq\frac{992}{12}\\\\n=82~rest~8,~~~~dar~n\in N\\\\\implies~n=82+1=83\\\\\boxed{\bf n=83~de~zale}\\\\Verificare:\\\\83\times20-(83-1)\times8=\\\\=83\times20-(83-1)\times8=\\\\=83\times20-82\times8=\\\\=1660-656=1004~mm\\\\\1004~mm > 1~metru\\\\\implies \boxed{\bf83~de~zale~este~cel~mai~mic~numar~de~zale.}[/tex]