С-17 Умножение и деление обыкновенных дробей. Вариант I. 1. Вычислите: а) 3/4 * 5/7; б) 4/11 * 3/4... 2. Вычислите: а) 2 * (14/15 : 2/3)...

**1. Вычислите:** а) $\frac{3}{4} \cdot \frac{5}{7} = \frac{3 \cdot 5}{4 \cdot 7} = \frac{15}{28}$ б) $\frac{4}{11} \cdot \frac{3}{4} = \frac{\uline{4} \cdot 3}{11 \cdot \uline{4}} = \frac{3}{11}$ в) $\frac{5}{7} \cdot \frac{14}{19} = \frac{5 \cdot \uline{14}^{2}}{\uline{7}_{1} \cdot 19} = \frac{10}{19}$ г) $\left(\frac{3}{5}\right)^{2} = \frac{3^{2}}{5^{2}} = \frac{9}{25}$ д) $\frac{4}{5} : \frac{3}{7} = \frac{4}{5} \cdot \frac{7}{3} = \frac{28}{15} = 1\frac{13}{15}$ е) $\frac{15}{8} : \frac{5}{4} = \frac{15}{8} \cdot \frac{4}{5} = \frac{\uline{15}^{3} \cdot \uline{4}^{1}}{\uline{8}_{2} \cdot \uline{5}_{1}} = \frac{3}{2} = 1\frac{1}{2}$ ж) $\frac{4}{9} : 2 = \frac{4}{9} \cdot \frac{1}{2} = \frac{\uline{4}^{2} \cdot 1}{9 \cdot \uline{2}_{1}} = \frac{2}{9}$ з) $6 : \frac{3}{5} = 6 \cdot \frac{5}{3} = \frac{\uline{6}^{2} \cdot 5}{\uline{3}_{1}} = 10$ **2. Вычислите:** а) $2 \cdot \left(\frac{14}{15} : \frac{2}{3}\right) = 2 \cdot \left(\frac{14}{15} \cdot \frac{3}{2}\right) = 2 \cdot \frac{\uline{14}^{7} \cdot \uline{3}^{1}}{\uline{15}_{5} \cdot \uline{2}_{1}} = 2 \cdot \frac{7}{5} = \frac{14}{5} = 2\frac{4}{5}$ б) $\frac{12}{11} : \frac{3}{4} \cdot \frac{11}{24} = \frac{12}{11} \cdot \frac{4}{3} \cdot \frac{11}{24} = \frac{\uline{12} \cdot 4 \cdot \uline{11}}{\uline{11} \cdot 3 \cdot \uline{24}_{2}} = \frac{4}{3 \cdot 2} = \frac{\uline{4}^{2}}{6_{3}} = \frac{2}{3}$ в) $\frac{1}{2} \cdot \frac{2}{3} \cdot \frac{3}{4} \cdot \frac{4}{5} = \frac{1 \cdot \uline{2} \cdot \uline{3} \cdot \uline{4}}{\uline{2} \cdot \uline{3} \cdot \uline{4} \cdot 5} = \frac{1}{5}$