21 câu Trắc nghệm Toán 6 Bài 12: Phép chia phân số có đáp án

Đáp án B

Phân số nghịch đảo của phân số $\frac{5}{6}$ là $\frac{6}{5}$

Đáp án A

Phân số nghịch đảo của phân số $\frac{-4}{3}$ là $\frac{3}{-4}$

Đáp án C

Phân số nghịch đảo của số −3 là $\frac{1}{-3}$

Đáp án B

Phân số nghịch đảo của số 6 là $\frac{1}{6}$

Đáp án D

$\frac{2}{3}:\frac{1}{2}=\frac{2}{3}.\frac{2}{1}=\frac{4}{3}$

Đáp án C

$\frac{2}{9}:\frac{3}{4}=\frac{2}{9}.\frac{4}{3}=\frac{8}{27}$

Đáp án D

$\frac{\left(-7\right)}{6}:\left(-\frac{14}{3}\right)=\frac{-7}{6}.\frac{-3}{14}=\frac{1.1}{2.2}=\frac{1}{4}$

Đáp án B

$\left(-\frac{3}{4}\right):\left(-\frac{33}{8}\right)=\frac{-3}{4}.\frac{-8}{33}=\frac{\left(-3\right).\left(-8\right)}{4.33}=\frac{24}{132}=\frac{2}{11}$

Đáp án B

$$\begin{gathered} \frac{13}{25}:x=\frac{5}{26} \\ x=\frac{13}{25}:\frac{5}{26} \\ x=\frac{13}{25}.\frac{26}{5} \\ x=\frac{338}{125} \end{gathered}$$

Đáp án D

$$\begin{gathered} \frac{3}{8}:x=-\frac{1}{2} \\ x=\frac{3}{8}:\left(-\frac{1}{2}\right) \\ x=\frac{3}{8}.\left(-2\right) \\ x=\frac{-3}{4} \end{gathered}$$

Vậy $x=-\frac{3}{4}$.

Đáp án B

$$\begin{gathered} \left(-\frac{3}{4}\right).x=\frac{4}{15} \\ x=\frac{4}{15}:\left(\frac{-3}{5}\right) \\ x=\frac{4}{15}.\frac{5}{-3} \\ x=\frac{-4}{9} \end{gathered}$$

Vậy $x = -\frac{4}{9}$

Đáp án A

$$\begin{gathered} \left(-\frac{4}{3}\right).x=\frac{15}{16} \\ x=\frac{15}{16}:\left(-\frac{4}{3}\right) \\ x=\frac{15}{16}.\frac{-3}{4} \\ x=-\frac{45}{64} \end{gathered}$$

Vậy $x = -\frac{45}{64}$

Đáp án C

$$\begin{gathered} \frac{2}{3}:\frac{7}{12}:\frac{4}{18} \\ =\left(\frac{2}{3}:\frac{7}{12}\right):\frac{4}{18} \\ =\left(\frac{2}{3}.\frac{12}{7}\right):\frac{4}{18} \\ =\frac{8}{7}.\frac{18}{4} \\ =\frac{36}{7} \end{gathered}$$

Đáp án D

$$\begin{gathered} \left(\frac{11}{15}.\frac{35}{44}\right):\left(\frac{1}{7}.\frac{4}{13}\right) \\ =\frac{7}{12}:\frac{4}{91} \\ =\frac{7}{12}.\frac{91}{4} \\ =\frac{637}{48} \end{gathered}$$

Đáp án A

$$\begin{gathered} M=\frac{5}{6}:{\left(\frac{5}{2}\right)}^2+\frac{7}{15} \\ M= \frac{5}{6}:\frac{25}{4}+\frac{7}{15} \\ M= \frac{5}{6}.\frac{4}{25}+\frac{7}{15} \\ M= \frac{1.2}{3.5}+\frac{7}{15} \\ M= \frac{2}{15}+\frac{7}{15} \\ M= \frac{9}{15}=\frac{3}{5} \end{gathered}$$

Khi đó a = 3 , b = 5 nên a + b = 8

Đáp án C 

$$\begin{gathered} M=\left(\frac{4}{9}-\frac{7}{11}\right):\frac{4}{9}-\frac{3}{11} \\ =\frac{-19}{99}:\frac{4}{9}-\frac{3}{11} \\ =\frac{-19}{99}.\frac{9}{4}-\frac{3}{11} \\ =\frac{-19}{44}-\frac{3}{11} \\ =\frac{-31}{44} \end{gathered}$$

Vì $a>0$ . Nên khi đó a = 31,b = -44 nên $b - a = -44-31=-75$

Đáp án A

$$\begin{gathered} N=\frac{{\displaystyle \frac{4}{17}}-{\displaystyle \frac{4}{49}}-{\displaystyle \frac{4}{131}}}{{\displaystyle \frac{3}{17}}-{\displaystyle \frac{3}{49}}-{\displaystyle \frac{3}{131}}}=\frac{4.{\displaystyle \frac{1}{17}}-4.{\displaystyle \frac{1}{49}}-4.{\displaystyle \frac{1}{131}}}{3.{\displaystyle \frac{1}{17}}-3.{\displaystyle \frac{1}{49}}-3.{\displaystyle \frac{1}{131}}} \\ =\frac{4\left({\displaystyle \frac{1}{17}}-{\displaystyle \frac{1}{49}}-{\displaystyle \frac{1}{131}}\right)}{3\left(\frac{1}{17}-\frac{1}{49}-\frac{1}{131}\right)}=\frac{4}{3} \end{gathered}$$

Đáp án C

$$\begin{gathered} A=\frac{{\displaystyle \frac{2}{5}}+{\displaystyle \frac{2}{7}}+{\displaystyle \frac{2}{17}}-{\displaystyle \frac{2}{395}}}{{\displaystyle \frac{3}{5}}+{\displaystyle \frac{3}{7}}+{\displaystyle \frac{3}{17}}-{\displaystyle \frac{3}{395}}} \\ =\frac{2.{\displaystyle \frac{1}{5}}+2.{\displaystyle \frac{1}{7}}+2.{\displaystyle \frac{}{17}}-2{\displaystyle \frac{1}{395}}}{3.{\displaystyle \frac{1}{5}}+3.{\displaystyle \frac{1}{7}}+3.{\displaystyle \frac{1}{17}}-3.{\displaystyle \frac{1}{195}}} \\ =\frac{2\left({\displaystyle \frac{1}{5}}+{\displaystyle \frac{1}{7}}+{\displaystyle \frac{1}{17}}-{\displaystyle \frac{1}{395}}\right)}{3\left(\frac{1}{5}+\frac{1}{7}+\frac{1}{17}-\frac{1}{395}\right)}=\frac{2}{3} \end{gathered}$$

Đáp án A

$$\begin{gathered} P=\left(\frac{7}{20}+\frac{11}{15}-\frac{15}{12}\right):\left(\frac{11}{20}-\frac{26}{45}\right) \\ P=\left(\frac{21}{60}+\frac{44}{60}-\frac{75}{60}\right):\left(\frac{99}{180}-\frac{104}{180}\right) \\ P=\frac{-10}{60}:\frac{-5}{180}=\frac{-10}{60}.\frac{180}{-5}=6 \end{gathered}$$

$$\begin{gathered} Q=\frac{5-{\displaystyle \frac{5}{8}}+{\displaystyle \frac{5}{9}}-{\displaystyle \frac{5}{27}}}{8-{\displaystyle \frac{8}{3}}+{\displaystyle \frac{8}{9}}-{\displaystyle \frac{8}{27}}}:\frac{15-{\displaystyle \frac{15}{11}}+{\displaystyle \frac{15}{121}}}{16-{\displaystyle \frac{16}{11}}+{\displaystyle \frac{16}{121}}} \\ Q=\frac{5\left(1-{\displaystyle \frac{1}{3}}+{\displaystyle \frac{1}{9}}-{\displaystyle \frac{1}{27}}\right)}{8\left(1-\frac{1}{3}+\frac{1}{9}-\frac{1}{27}\right)}:\frac{15\left(1-{\displaystyle \frac{1}{11}}+{\displaystyle \frac{1}{121}}\right)}{16\left(1-\frac{1}{11}+\frac{1}{121}\right)} \\ Q=\frac{5}{8}:\frac{15}{16}=\frac{5}{8}.\frac{16}{15}=\frac{2}{3} \end{gathered}$$

Vì $6>\frac{2}{3}$ nên $P>Q$

Đáp án B

$$\begin{gathered} C=\frac{4}{5}:\left(\frac{4}{5}.\frac{-5}{4}\right):\left(\frac{16}{25}-\frac{1}{5}\right) \\ =\frac{4}{5}:\left(-1\right):\frac{11}{25} \\ =\frac{4}{5}.\left(-1\right).\frac{25}{11} \\ =-\frac{20}{11} \end{gathered}$$

$$\begin{gathered} D=\frac{{\displaystyle \frac{15}{8}}-{\displaystyle \frac{15}{16}}-{\displaystyle \frac{15}{32}}+{\displaystyle \frac{15}{64}}}{3-{\displaystyle \frac{3}{2}}-{\displaystyle \frac{3}{4}}+{\displaystyle \frac{3}{8}}} \\ =\frac{{\displaystyle \frac{15}{8}}\left({\displaystyle 1}-{\displaystyle \frac{1}{2}}-{\displaystyle \frac{1}{4}}+{\displaystyle \frac{1}{8}}\right)}{3.\left(1-{\displaystyle \frac{1}{2}}-{\displaystyle \frac{1}{4}}+{\displaystyle \frac{1}{8}}\right)} \\ =\frac{{\displaystyle \frac{15}{8}}}{3} \\ =\frac{5}{8} \end{gathered}$$

Vì $\frac{5}{8}>-\frac{20}{11}$ nên D > C

Đáp án D

$$\begin{gathered} \left(x+\frac{1}{4}-\frac{1}{3}\right):\left(2+\frac{1}{6}-\frac{1}{4}\right)=\frac{7}{46} \\ =\left(x+\frac{1}{4}-\frac{1}{3}\right):\frac{23}{12}=\frac{7}{46} \\ x+\frac{1}{4}-\frac{1}{3}=\frac{7}{46}.\frac{12}{23} \\ x+\frac{1}{4}-\frac{1}{3}=\frac{7}{24} \\ x=\frac{7}{24}-\frac{1}{4}+\frac{1}{3} \\ x=\frac{3}{8} \end{gathered}$$

Vậy $x = \frac{3}{8}$.