Răspuns :
P dreptunghi = 76 cm
L = ? l = ?
L = 2 • 3 • l => L = 6 • 38/7 => 228/7
P dreptunghi = 2(L + l ) => 2 ( 2 • 3 • l + l ) => 2 ( 6 • l + l ) => 2 • 7 l => 14 • l
76 cm = 14 • l
l = 76 / 14 simplificam cu 2
l = 38 / 7
Perimetrul dreptunghi = 76 cm
2l+2L=76
L=2 + 3l
2l + 2(2+3l) = 76
2 l + 4 +6l=76
8l = 76-4
8l = 72
l = 72/8 = 9
l=9 cm
L=2 + 3l = 2 + 3x9= 29
L=29 cm
verificare
2 x 9 + 2 x29 = 18 + 58 += 76 cm
