488.
1) $2: \frac{3}{5} + \frac{3}{5} : 2 + 1 \frac{1}{2} : 6 + 6 : 1 \frac{1}{2} = \frac{2 \cdot 5}{3} + \frac{3}{5 \cdot 2} + \frac{3}{2 \cdot 6} + \frac{6 \cdot 2}{3} = \frac{10}{3} + \frac{3}{10} + \frac{1}{4} + 4 = 3 \frac{1}{3} + \frac{3}{10} + \frac{1}{4} + 4 = 7 \frac{20+18+15}{60} = 7 \frac{53}{60}$
2) $6 \frac{1}{4} \cdot 8 - 3 \frac{2}{3} \cdot 5 \frac{1}{2} + 2 \frac{2}{5} \cdot 4 \frac{7}{12} = \frac{25 \cdot 8}{4} - \frac{11 \cdot 11}{3 \cdot 2} + \frac{12 \cdot 55}{5 \cdot 12} = 50 - \frac{121}{6} + 11 = 61 - 20 \frac{1}{6} = 40 \frac{5}{6}$
3) $2 \frac{1}{2} \cdot 48 - 3 \frac{3}{8} \cdot \frac{1}{18} + 5 \frac{5}{12} \cdot \frac{7}{36} = \frac{5 \cdot 48}{2} - \frac{27 \cdot 1}{8 \cdot 18} + \frac{65 \cdot 7}{12 \cdot 36} = 120 - \frac{3}{16} + \frac{455}{432} = 120 - \frac{81}{432} + 1 \frac{23}{432} = 121 - \frac{58}{432} = 120 \frac{432-58}{432} = 120 \frac{374}{432} = 120 \frac{187}{216}$
4) $13 \frac{1}{2} : 1 \frac{1}{8} + 16 \frac{1}{2} : 1 \frac{5}{11} + 19 \frac{1}{4} : \frac{4}{25} = \frac{27 \cdot 8}{2 \cdot 9} + \frac{33 \cdot 11}{2 \cdot 16} + \frac{77 \cdot 25}{4 \cdot 4} = 12 + \frac{363}{32} + \frac{1925}{16} = 12 + 11 \frac{11}{32} + 120 \frac{5}{16} = 143 + \frac{11+10}{32} = 143 \frac{21}{32}$
489.
1) $(3 \frac{1}{2} - 2 \frac{2}{3} + 5 \frac{5}{6} + 4 \frac{3}{4}) \cdot 24 = (\frac{7}{2} - \frac{8}{3} + \frac{35}{6} + \frac{19}{4}) \cdot 24 = 84 - 64 + 140 + 114 = 274$
2) $(5 \frac{3}{8} + 18 \frac{1}{2} - 7 \frac{5}{24}) : 16 \frac{2}{3} = (5 \frac{9}{24} + 18 \frac{12}{24} - 7 \frac{5}{24}) : \frac{50}{3} = 16 \frac{16}{24} : \frac{50}{3} = 16 \frac{2}{3} : \frac{50}{3} = \frac{50}{3} : \frac{50}{3} = 1$
3) $(12 \frac{5}{12} + 1 \frac{2}{3} - 3 \frac{5}{6} + 2 \frac{3}{4}) : (2 \frac{1}{2} \cdot \frac{2}{5} - \frac{7}{9}) = (12 \frac{5}{12} + 1 \frac{8}{12} - 3 \frac{10}{12} + 2 \frac{9}{12}) : (1 - \frac{7}{9}) = 13 \frac{1}{12} - 3 \frac{10}{12} + 2 \frac{9}{12} : \frac{2}{9} = (9 \frac{3}{12} + 2 \frac{9}{12}) : \frac{2}{9} = 12 : \frac{2}{9} = \frac{12 \cdot 9}{2} = 54$
4) $48 \frac{3}{5} : 6 \frac{3}{4} \cdot \frac{5}{12} - 2 \frac{5}{6} + 1 \frac{75}{94} \cdot (1 \frac{1}{2} \cdot 1 \frac{1}{3} - 13 : 26) = \frac{243 \cdot 4 \cdot 5}{5 \cdot 27 \cdot 12} - 2 \frac{5}{6} + \frac{169}{94} \cdot (\frac{3 \cdot 4}{2 \cdot 3} - \frac{1}{2}) = \frac{9 \cdot 4}{12} - 2 \frac{5}{6} + \frac{169}{94} \cdot (2 - 0.5) = 3 - 2 \frac{5}{6} + \frac{169 \cdot 1.5}{94} = \frac{1}{6} + \frac{169 \cdot 3}{94 \cdot 2} = \frac{1}{6} + \frac{507}{188} = \frac{94 + 1521}{564} = \frac{1615}{564} = 2 \frac{487}{564}$
927.
1) $\frac{5}{7} \cdot (\frac{21}{20} - \frac{7}{30}) + \frac{16}{21} : \frac{8}{7} = \frac{5}{7} \cdot \frac{63-14}{60} + \frac{16 \cdot 7}{21 \cdot 8} = \frac{5 \cdot 49}{7 \cdot 60} + \frac{2}{3} = \frac{7}{12} + \frac{8}{12} = \frac{15}{12} = 1 \frac{1}{4}$
2) $\frac{4}{45} : (\frac{12}{25} - \frac{4}{15}) + \frac{15}{16} \cdot \frac{4}{15} = \frac{4}{45} : \frac{36-20}{75} + \frac{1}{4} = \frac{4 \cdot 75}{45 \cdot 16} + \frac{1}{4} = \frac{5}{12} + \frac{3}{12} = \frac{8}{12} = \frac{2}{3}$
3) $2 : 2 \frac{2}{3} + 1 \frac{4}{5} \cdot 3 \frac{1}{3} - 2 \frac{5}{6} = 2 : \frac{8}{3} + \frac{9}{5} \cdot \frac{10}{3} - 2 \frac{5}{6} = \frac{3}{4} + 6 - 2 \frac{5}{6} = 6 \frac{9}{12} - 2 \frac{10}{12} = 3 \frac{11}{12}$
4) $3 : 3 \frac{3}{4} + 2 \frac{2}{5} \cdot 2 \frac{1}{2} - 3 \frac{5}{6} = 3 : \frac{15}{4} + \frac{12 \cdot 5}{5 \cdot 2} - 3 \frac{5}{6} = \frac{4}{5} + 6 - 3 \frac{5}{6} = 6 \frac{24}{30} - 3 \frac{25}{30} = 2 \frac{29}{30}$
928.
1) $96 \cdot \frac{7}{125} + 97 \cdot \frac{11}{125} - 192 \cdot \frac{9}{125} = \frac{672 + 1067 - 1728}{125} = \frac{1739 - 1728}{125} = \frac{11}{125}$
2) $3 \frac{12}{19} \cdot 4 \frac{3}{23} + 1 \frac{4}{19} \cdot 5 \frac{7}{23} - 1 \frac{8}{19} = \frac{69 \cdot 95}{19 \cdot 23} + \frac{23 \cdot 122}{19 \cdot 23} - \frac{27}{19} = \frac{15 + 122 - 27}{19} = \frac{110}{19} = 5 \frac{15}{19}$
501.
1) Находим урожай при обычной посадке: $150 \cdot \frac{3}{5} = 30 \cdot 3 = 90$ ц с 1 га.
2) Разница урожайности на 1 га: $150 - 90 = 60$ ц.
3) Разница с 15 га: $60 \cdot 15 = 900$ ц.
**Ответ: 900 ц.**
510.
Пусть $x$ — количество рабочих во всем заводе.
1-й цех: $\frac{2}{5}x$
2-й цех: $\frac{2}{5}x : 1 \frac{1}{2} = \frac{2}{5}x : \frac{3}{2} = \frac{4}{15}x$
3-й цех: 100 человек.
Уравнение: $\frac{2}{5}x + \frac{4}{15}x + 100 = x$
$\frac{6+4}{15}x + 100 = x$
$\frac{10}{15}x + 100 = x$
$\frac{2}{3}x + 100 = x$
$\frac{1}{3}x = 100$
$x = 300$
**Ответ: 300 рабочих.**
