Ответ:

  1. \(4 \times 2\frac{4}{5}=4\times\frac{14}{5}=\frac{56}{5}=11\frac{1}{5}\).

  2. \(2 \times 5\frac{7}{12}=2\times\frac{67}{12}=\frac{134}{12}=11\frac{1}{6}\).

  3. \(1\frac{7}{8}\times 6=\frac{15}{8}\times 6=\frac{90}{8}=11\frac{1}{4}\).

  4. \(2\frac{3}{10}\times 5=\frac{23}{10}\times 5=\frac{115}{10}=11\frac{1}{2}\).

Ответ: 4 × 2 4/5 → 11 1/5; 2 × 5 7/12 → 11 1/6; 1 7/8 × 6 → 11 1/4; 2 3/10 × 5 → 11 1/2.