Trắc nghiệm bài tập theo tuần Toán 7-Tuần 3 có đáp án

$-6.\left(-\frac{2}{3}\right)\mathrm{.0,25}=4.\frac{1}{4}=1$

$-\frac{15}{4}.\left(\frac{-7}{15}\right).\left(-2\frac{2}{5}\right)=\frac{7}{4}.\left(-\frac{12}{5}\right)=-\frac{21}{5}$

$\left(-2\frac{1}{5}\right).\left(-\frac{9}{11}\right).\left(-1\frac{1}{14}\right).\frac{2}{5}=\left(-\frac{11}{5}\right).\left(-\frac{9}{11}\right).\left(-\frac{15}{14}\right).\frac{2}{5}=-\frac{27}{35}$

$\left(-5\frac{1}{2}\right).\left(-\frac{1}{2}\right)-\frac{2}{3}.\left(-\frac{2}{3}\right)=\left(-\frac{11}{2}\right).\left(-\frac{1}{2}\right)+\frac{4}{9}=\frac{11}{4}+\frac{4}{9}=\frac{115}{36}$

$\left(1\frac{1}{4}\right).\left(-\frac{8}{15}\right)-\frac{3}{5}+\frac{2}{5}.\left(-\frac{3}{4}\right)=\left(\frac{5}{4}\right).\left(-\frac{8}{15}\right)-\frac{3}{5}-\frac{3}{10}=\left(-\frac{2}{3}\right)-\frac{3}{5}-\frac{3}{10}=-\frac{47}{30}$

$\left(-\mathrm{0,125}\right).(-16).\left(-\frac{8}{9}\right).\left(-\mathrm{0,25}\right)=\frac{1}{8}\mathrm{.16.}\frac{8}{9}.\frac{1}{4}=\frac{4}{9}$

$\frac{5}{8}+2\frac{1}{4}.1\frac{2}{3}-\frac{1}{4}.\frac{5}{6}=\frac{5}{8}+\frac{9}{4}.\frac{5}{3}-\frac{5}{24}=\frac{5}{4}.\left(\frac{1}{2}+3-\frac{1}{6}\right)=\frac{5}{4}.\frac{10}{3}=\frac{25}{6}$

$\left(13\frac{9}{11}:\frac{38}{49}-5\frac{2}{11}:\frac{38}{49}\right):\left(\frac{49}{38}.\frac{5}{11}\right)=\left\{\left(13+\frac{9}{11}\right).\frac{49}{38}-\left(5+\frac{2}{11}\right).\frac{49}{38}\right\}:\left(\frac{49}{38}.\frac{5}{11}\right)$

$\begin{array}{l}=\frac{49}{38}.\left(13-5+\frac{9}{11}-\frac{2}{11}\right):\left(\frac{49}{38}.\frac{5}{11}\right)=\frac{49}{38}.\left(8+\frac{7}{11}\right):\left(\frac{49}{38}.\frac{5}{11}\right)\\ =\left(8+\frac{7}{11}\right):\frac{5}{11}=19\end{array}$

$\frac{11}{30}+\frac{18}{35}.\left(\frac{35}{54}-\frac{49}{18}-\frac{28}{48}\right)=\frac{11}{30}+\left(\frac{18}{35}.\frac{35}{54}-\frac{18}{35}.\frac{49}{18}-\frac{18}{35}.\frac{28}{48}\right)$

$=\frac{11}{30}+\left(\frac{1}{3}-\frac{7}{5}-\frac{3}{10}\right)=\frac{11}{30}+\frac{-41}{30}=-1$

$\frac{-23}{39}.\frac{-13}{56}.\frac{70}{23}:\frac{125}{75}=\frac{5}{3.4}.\frac{3}{5}=\frac{1}{4}$

$\frac{-1}{10}+\frac{2}{5}x+\frac{7}{20}=\frac{1}{10}$

$\frac{2}{5}x=\frac{1}{10}-\frac{7}{20}+\frac{1}{10}$

$\begin{array}{l}\frac{2}{5}x=-\frac{3}{20}\\ x=-\frac{3}{8}\end{array}$

$-\frac{2}{3}:x+\frac{5}{8}=-\frac{7}{12}$

$\begin{array}{l}\frac{-2}{3}:x=-\frac{7}{12}-\frac{5}{8}\\ \frac{-2}{3}:x=-\frac{29}{24}\\ x=\frac{16}{29}\end{array}$

$\frac{5.18-10.27+15.36}{10.36-20.54+30.72}=\frac{5.18-\mathrm{5.18.3}+\mathrm{5.18.6}}{10.36-\mathrm{10.36.3}+\mathrm{10.36.6}}=\frac{5.18\left(1-3+6\right)}{10.36\left(1-3+6\right)}=\frac{1}{4}$

$\left(\frac{1}{2}-1\right)\left(\frac{1}{3}-1\right)\left(\frac{1}{4}-1\right)\mathrm{.....}\left(\frac{1}{1999}-1\right)=\frac{-1}{2}.\frac{-2}{3}.\frac{-3}{4}\mathrm{....}\frac{-1998}{1999}=\frac{1}{1999}$

$-1\frac{1}{2}.\left(-1\frac{1}{3}\right).\left(-1\frac{1}{4}\right)\mathrm{......}\left(-1\frac{1}{1999}\right)=\frac{-3}{2}.\frac{-4}{3}.\frac{-5}{4}\mathrm{.....}\frac{-2000}{1999}=1000$