Toán Lớp 7: 1) -9/34 . 17/4 2) 11/30 – 7/35 3) (-3,8) . (-65/28) 4) 21/5: -40/5
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Toán Lớp 7: 1) -9/34 . 17/4 2) 11/30 – 7/35 3) (-3,8) . (-65/28) 4) 21/5: -40/5
Comments ( 2 )
1)\frac{{ – 9}}{{34}} \times \frac{{17}}{4} = \frac{{ – 153}}{{136}} = \frac{{ – 9}}{8}\\
2)\frac{{11}}{{30}} – \frac{7}{{35}} = \left( {\frac{{11 \times 35}}{{30 \times 35}}} \right) – \left( {\frac{{7 \times 30}}{{35 \times 30}}} \right) = \frac{{385}}{{1050}} – \frac{{210}}{{1050}} = \frac{{175}}{{1050}} = \frac{1}{6}\\
3) – 3,8 \times \left( {\frac{{ – 65}}{{28}}} \right) = \frac{{ – 38}}{1} \times \left( {\frac{{ – 65}}{{28}}} \right) = \frac{{ – 103}}{{28}}\\
4)\frac{{21}}{5} \div \frac{{ – 40}}{5} = \frac{{21}}{5} \times \frac{5}{{ – 40}} = \frac{{105}}{{ – 200}} = \frac{{ – 21}}{{40}}
\end{array}\]