Réponse:
[tex]1. \: \: \: \frac{2}{7} + \frac{2}{7} + \frac{3}{8} \\ = \frac{4}{7} + \frac{3}{8} \\ = \frac{4 \times 8}{7 \times 8} + \frac{3 \times 7}{8 \times 7} \\ = \frac{32}{56} + \frac{21}{56} \\ = \frac{32 + 21}{56} \\ = \frac{53}{56} [/tex]
[tex]2. \: \: \: \frac{3}{8} + \frac{2}{7} + \frac{3}{8} + \frac{2}{7} \\ = \frac{6}{8} + \frac{4}{7} \\ = \frac{42}{56} + \frac{32}{56} \\ = \frac{74}{56} = \frac{37}{28} [/tex]
Le périmètre du rectangle ADEF est :
[tex]4 \times \frac{2}{7} + 2 \times \frac{3}{8} \\ = \frac{8}{7} + \frac{6}{8} \\ = \frac{64}{56} + \frac{42}{56} \\ = \frac{106}{64} \\ = \frac{53}{32} [/tex]
