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9. 计算.
(1) $-1\dfrac{7}{8} ÷ (-\dfrac{15}{16})$
(2) $(-3\dfrac{1}{4}) × \dfrac{4}{13} ÷ (-\dfrac{1}{2})$
(3) $(-\dfrac{1}{6} + \dfrac{1}{3} - \dfrac{1}{2}) ÷ (-\dfrac{1}{18})$
(4) $(-\dfrac{3}{8}) × (-3\dfrac{1}{8}) - \dfrac{3}{8} × (-4\dfrac{7}{8})$
(1) $-1\dfrac{7}{8} ÷ (-\dfrac{15}{16})$
(2) $(-3\dfrac{1}{4}) × \dfrac{4}{13} ÷ (-\dfrac{1}{2})$
(3) $(-\dfrac{1}{6} + \dfrac{1}{3} - \dfrac{1}{2}) ÷ (-\dfrac{1}{18})$
(4) $(-\dfrac{3}{8}) × (-3\dfrac{1}{8}) - \dfrac{3}{8} × (-4\dfrac{7}{8})$
答案
9. (1) 2 (2) 2 (3) 6 (4) 3
10. 某冷冻厂的一个冷库现在的室温是$-2°\mathrm{C}$,有一批食品,需要在$-30°\mathrm{C}$以下冷藏. 如果每小时能降温$4°\mathrm{C}$,那么需要几小时才能降到所需温度?
答案
10. 7小时
