Perimetrul dreptunghiului = 2 × ( L + latime) = L + 97 m
2 × L + 2 × l - L = 97 m
2 × L + 2 × l = l + 122 m
L + 2 × l = 97 m l × 2
2 × L + l = 122 m
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2 × L + 4 × l = 194 m → le scad
2 × L + l = 122 m
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/ 3 × l = 72 m ⇒ l = 72 : 3 ⇒ l = 24 m ( latimea)
L = 97 m - 2 × 24 m = 97 m - 48 m = 49 m ( lungimea)
sau:
122 m - 97 m = 25 m ⇒ L > latimea cu 25 m
2 × L + 2 × l = L + 97
L + 2 × l = 97
( l + 25 m ) + 2 × l = 97 m
3 × l = 97 - 25
l = 72 : 3 ⇒ l = 24 m = 2 400 cm ( latimea)
L = 24 m + 25 m = 49 m = 4 900 cm ( lungimea )