1) 7/40 + 11/60 = 2) 19/24 - 25/32 + (2/48 + 1/96) = 3) t - 11/18 = 11/12 - 5/9 4) 1/6 + 3/16 + 5/6 + 5/16 = 5) Сравнить 2/3 8/21; 3/8 17/40; 13/18 11/15

1) $\frac{7}{40} + \frac{11}{60} = \frac{21}{120} + \frac{22}{120} = \frac{43}{120}$ 2) $\frac{19}{24} - \frac{25}{32} + (\frac{2}{48} + \frac{1}{96}) = \frac{19 \cdot 4}{96} - \frac{25 \cdot 3}{96} + (\frac{2 \cdot 2}{96} + \frac{1}{96}) = \frac{76 - 75}{96} + \frac{4 + 1}{96} = \frac{1}{96} + \frac{5}{96} = \frac{6}{96} = \frac{1}{16}$ 3) $t - \frac{11}{18} = \frac{11}{12} - \frac{5}{9}$ $t - \frac{11}{18} = \frac{33 - 20}{36} = \frac{13}{36}$ $t = \frac{13}{36} + \frac{11}{18} = \frac{13}{36} + \frac{22}{36} = \frac{35}{36}$ 4) $\frac{1}{6} + \frac{3}{16} + \frac{5}{6} + \frac{5}{16} = (\frac{1}{6} + \frac{5}{6}) + (\frac{3}{16} + \frac{5}{16}) = \frac{6}{6} + \frac{8}{16} = 1 + \frac{1}{2} = 1\frac{1}{2}$ (или $1,5$) 5) Сравнение дробей: - $\frac{2}{3}$ и $\frac{8}{21}$: $\frac{2 \cdot 7}{21} = \frac{14}{21}$. Так как $14 > 8$, то $\frac{2}{3} > \frac{8}{21}$. - $\frac{3}{8}$ и $\frac{17}{40}$: $\frac{3 \cdot 5}{40} = \frac{15}{40}$. Так как $15 < 17$, то $\frac{3}{8} < \frac{17}{40}$. - $\frac{13}{18}$ и $\frac{11}{15}$: Общий знаменатель $90$: $\frac{13 \cdot 5}{90} = \frac{65}{90}$, $\frac{11 \cdot 6}{90} = \frac{66}{90}$. Так как $65 < 66$, то $\frac{13}{18} < \frac{11}{15}$.