1) 11/20 : 11/20; 2) 4/35 : 4/35; 3) 3/4 : 1/4; 4) 7/9 : 1/9; 5) 15/16 : 5/16.

1. \(\dfrac{11}{20}:\dfrac{11}{20}=\dfrac{11}{20}\cdot\dfrac{20}{11}=1\).
2. \(\dfrac{4}{35}:\dfrac{4}{35}=\dfrac{4}{35}\cdot\dfrac{35}{4}=1\).
3. \(\dfrac{3}{4}:\dfrac{1}{4}=\dfrac{3}{4}\cdot\dfrac{4}{1}=3\).
4. \(\dfrac{7}{9}:\dfrac{1}{9}=\dfrac{7}{9}\cdot\dfrac{9}{1}=7\).
5. \(\dfrac{15}{16}:\dfrac{5}{16}=\dfrac{15}{16}\cdot\dfrac{16}{5}=3\).

Ответ: 1) 1; 2) 1; 3) 3; 4) 7; 5) 3.