Question

7．大于$\frac{1}{8}$而小于$\frac{7}{8}$的真分?jǐn)?shù)有（　�。﹤�(gè)．

• A． 5
• B． 2
• C． 3
• D． 無數(shù)

Answer 1

分析 根據(jù)分?jǐn)?shù)的基本性質(zhì)可知，$\frac{1}{8}$=$\frac{2}{16}$=$\frac{3}{24}$…，$\frac{2}{8}$=$\frac{4}{16}$=$\frac{6}{24}$…，…，$\frac{6}{8}$=$\frac{12}{16}$=$\frac{18}{24}$=…，$\frac{7}{8}$=$\frac{14}{16}$=$\frac{21}{24}$…．所以大于$\frac{1}{8}$而小于$\frac{7}{8}$的真分?jǐn)?shù)有$\frac{1}{8}$、$\frac{2}{16}$=$\frac{3}{24}$…，$\frac{4}{16}$、$\frac{6}{24}$…，$\frac{12}{16}$、$\frac{18}{24}$…．即有無數(shù)個(gè)．

解答 解：由于$\frac{1}{8}$＜$\frac{2}{8}$＜…＜$\frac{6}{8}$$＜\frac{7}{8}$，
又$\frac{1}{8}$=$\frac{2}{16}$=$\frac{3}{24}$…，$\frac{2}{8}$=$\frac{4}{16}$=$\frac{6}{24}$…，…，$\frac{6}{8}$=$\frac{12}{16}$=$\frac{18}{24}$=…，$\frac{7}{8}$=$\frac{14}{16}$=$\frac{21}{24}$…．
所以大于$\frac{1}{8}$而小于$\frac{7}{8}$的真分?jǐn)?shù)有$\frac{1}{8}$、$\frac{2}{16}$=$\frac{3}{24}$…，$\frac{4}{16}$、$\frac{6}{24}$…，$\frac{12}{16}$、$\frac{18}{24}$…．
即有無數(shù)個(gè)．
故選：D．

點(diǎn)評 分母為8的大于$\frac{1}{8}$而小于$\frac{7}{8}$的真分?jǐn)?shù)有5個(gè)．