11. 4/15 * 55/6 =

11. $$\frac{4}{15} \times \frac{55}{6} = \frac{4 \times 55}{15 \times 6} = \frac{220}{90} = \frac{22}{9} = 2\frac{4}{9}$$

Ответ: $$2\frac{4}{9}$$