6) 4\frac{1}{2} : 2\frac{2}{5} = 3\frac{1}{4} : t;

Найдем неизвестный член пропорции t.

$$4\frac{1}{2} : 2\frac{2}{5} = 3\frac{1}{4} : t$$

$$\frac{9}{2} : \frac{12}{5} = \frac{13}{4} : t$$

$$t = \frac{\frac{12}{5} \times \frac{13}{4}}{\frac{9}{2}}$$\

$$t = \frac{\frac{156}{20}}{\frac{9}{2}}$$\

$$t = \frac{156}{20} \times \frac{2}{9}$$\

$$t = \frac{312}{180}$$\

$$t = \frac{26}{15}$$\

$$t = 1\frac{11}{15}$$\

Ответ: $$1\frac{11}{15}$$