Question

Câu 13: Thực hiện phép tính \( \frac{3}{4} - \frac{1}{5} \left( \frac{4}{7} + \frac{3}{5} : \frac{-7}{5} \right) \) kết quả là

A. \( -\frac{3}{70} \).

B. \( -\frac{30}{7} \).

C. \( \frac{30}{7} \).

D. \( \frac{3}{70} \).

Câu 14: Thực hiện phép tính \( \left( \frac{67}{111} + \frac{2}{33} - \frac{15}{117} \right) \left( \frac{1}{3} - \frac{1}{4} - \frac{1}{12} \right) \) kết quả là

A. \( \frac{5}{12} \).

B. \( \frac{1}{12} \).

C. \( 0 \).

D. \( \frac{67}{111} \).

Câu 15: Thực hiện phép tính \( \left( \frac{4}{3} + \frac{8}{3} \right) \left( \frac{7}{4} - 6 : \frac{4}{5} \right) \left( \frac{7}{5} + \frac{12}{5} \right) \) kết quả là

A. \( \frac{6}{19} \).

B. \( \frac{5}{19} \).

C. \( -\frac{5}{19} \).

D. \( -\frac{19}{5} \).

Answer 1

Câu 13:

\(\dfrac{3}{4}\cdot\left[\dfrac{1}{5}-\left(\dfrac{4}{7}+\dfrac{3}{5}:\dfrac{-7}{5}\right)\right]\)

\(=\dfrac{3}{4}\cdot\left(\dfrac{1}{5}-\dfrac{4}{7}+\dfrac{3}{5}\cdot\dfrac{5}{7}\right)\)

\(=\dfrac{3}{4}\left(\dfrac{1}{5}-\dfrac{4}{7}+\dfrac{3}{7}\right)=\dfrac{3}{4}\left(\dfrac{1}{5}-\dfrac{1}{7}\right)\)

\(=\dfrac{3}{4}\cdot\dfrac{2}{35}=\dfrac{3}{2\cdot35}=\dfrac{3}{70}\)

=>Chọn D

Câu 14:

\(\left(\dfrac{67}{111}+\dfrac{2}{33}-\dfrac{15}{117}\right)\left(\dfrac{1}{3}-\dfrac{1}{4}-\dfrac{1}{12}\right)\)

\(=\left(\dfrac{67}{111}+\dfrac{2}{33}-\dfrac{15}{117}\right)\left(\dfrac{4}{12}-\dfrac{3}{12}-\dfrac{1}{12}\right)\)

\(=\left(\dfrac{67}{111}+\dfrac{2}{33}-\dfrac{5}{39}\right)\cdot0=0\)

=>Chọn C

Câu 15:

\(\left(\dfrac{4}{3}+\dfrac{8}{3}\right)\left(\dfrac{7}{4}-\dfrac{6}{4}\right):\left(\dfrac{7}{5}+\dfrac{12}{5}\right)\)

\(=\dfrac{12}{3}\cdot\dfrac{1}{4}:\dfrac{19}{5}\)

\(=\dfrac{12}{12}\cdot\dfrac{5}{19}=\dfrac{5}{19}\)

=>Chọn B