4. Вычислите удобным способом. a) 5,53 * 8,09 + 1,91 * 5,53 б) 15/36 * 8/14 + 3 13/14 * 15/36

a) \(5,53 \cdot 8,09 + 1,91 \cdot 5,53 = 5,53 \cdot (8,09 + 1,91) = 5,53 \cdot 10 = 55,3\) б) \(\frac{15}{36} \cdot \frac{8}{14} + 3\frac{13}{14} \cdot \frac{15}{36} = \frac{15}{36} \cdot \frac{8}{14} + \frac{55}{14} \cdot \frac{15}{36} = \frac{15}{36} \cdot (\frac{8}{14} + \frac{55}{14}) = \frac{15}{36} \cdot \frac{63}{14} = \frac{15}{36} \cdot \frac{9 \cdot 7}{2 \cdot 7} = \frac{15}{36} \cdot \frac{9}{2} = \frac{5 \cdot 3}{12 \cdot 3} \cdot \frac{9}{2} = \frac{5}{4 \cdot 3} \cdot \frac{3 \cdot 3}{2} = \frac{5}{4} \cdot \frac{3}{2} = \frac{15}{8} = 1\frac{7}{8}\) Ответ: **15/8** или **1 13/8**