1.Viết bảng nhân 9 .
2.Tính
\(\frac{2}{5}+\frac{3}{6}\)
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Phép tính nào dưới đây là đúng?
(A) \(\frac{2}{3} + \frac{{ - 4}}{6} = \frac{{ - 2}}{6}\)
(B) \(\frac{2}{3}.\frac{{ - 1}}{5} = \frac{{3 - 2}}{5}\)
(C) \(\frac{2}{3} - \frac{3}{5} = \frac{1}{{15}}\)
(D) \(\frac{3}{5}:\frac{3}{{ - 5}} = - \frac{9}{{25}}\)
(A) \(\frac{2}{3} + \frac{{ - 4}}{6} = \frac{4}{6} + \frac{{ - 4}}{6} = 0\) => A sai
(B) \(\frac{2}{3}.\frac{{ - 1}}{5} = \frac{{ - 2}}{{15}}\) mà \(\frac{{3 - 2}}{5} = \frac{1}{5}\) => B sai
(C) \(\frac{2}{3} - \frac{3}{5} = \frac{{10}}{{15}} - \frac{9}{{15}} = \frac{1}{{15}}\) => C đúng
(D) \(\frac{3}{5}:\frac{3}{{ - 5}} = \frac{3}{5}.\frac{{ - 5}}{3} = \frac{{ - 15}}{{15}} = - 1\) => D sai
=> Chọn C.
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Toán lớp 7: câu 3, Các phép tính với số hữu tỉ
\(\frac{-2}{6}+\frac{-8}{6}=???\)
\(\frac{8}{-9}-\frac{9}{-3}=???\)
\(\frac{2}{5}\)nhân \(\frac{-2}{-5}\) = ???
\(\frac{6}{150}:\frac{6}{-150}=???\)
\(-\frac{2}{6}+\frac{-8}{6}=\frac{-1}{3}+\frac{-4}{3}=\frac{-5}{3}\)
\(\frac{8}{-9}-\frac{9}{-3}=-\frac{8}{9}-\frac{-9}{3}=-\frac{8}{9}-\frac{-27}{9}=\frac{19}{9}\)
\(\frac{2}{5}\cdot\frac{-2}{-5}=\frac{2}{5}\cdot\frac{2}{5}=\frac{4}{25}\)
\(\frac{6}{150}:\frac{6}{-150}=\frac{6}{150}\cdot\frac{-150}{6}=-1\)
1.Tính bằng cách hợp lí :
a)\(\left(\frac{-4}{9}+\frac{3}{5}\right):\frac{5}{6}+\left(\frac{1}{5}+\frac{5}{9}\right):\frac{5}{6}\)
b)\(\frac{1}{3^2}-\left(\frac{1}{3}\right)^2.\left(\frac{-1}{3}\right)^2\)
Tính giá trị các biểu thức sau theo cách có dùng tính chất phép tính phân số:
a) \(\frac{2}{3} + \frac{{ - 2}}{5} + \frac{{ - 5}}{6} - \frac{{13}}{{10}};\)
b) \(\frac{{ - 3}}{7}.\frac{{ - 1}}{9} + \frac{7}{{ - 18}}.\frac{{ - 3}}{7} + \frac{5}{6}.\frac{{ - 3}}{7}\)
a)
\(\begin{array}{l}\frac{2}{3} + \frac{{ - 2}}{5} + \frac{{ - 5}}{6} - \frac{{13}}{{10}}\\ = \frac{2}{3} + \frac{{ - 5}}{6} + \frac{{ - 2}}{5} - \frac{{13}}{{10}}\\ = \left( {\frac{2}{3} + \frac{{ - 5}}{6}} \right) + \left( {\frac{{ - 2}}{5} - \frac{{13}}{{10}}} \right)\\ = \left( {\frac{4}{6} + \frac{{ - 5}}{6}} \right) + \left( {\frac{{ - 4}}{{10}} - \frac{{13}}{{10}}} \right)\\ = \frac{{ - 1}}{6} + \frac{{ - 17}}{{10}}\\ = \frac{{ - 5}}{{30}} + \frac{{ - 51}}{{30}}\\ = \frac{{ - 56}}{{30}}\\ = \frac{{ - 28}}{{15}}\end{array}\)
b)
\(\begin{array}{l}\frac{{ - 3}}{7}.\frac{{ - 1}}{9} + \frac{7}{{ - 18}}.\frac{{ - 3}}{7} + \frac{5}{6}.\frac{{ - 3}}{7}\\ = \frac{{ - 3}}{7}.\left( {\frac{{ - 1}}{9} + \frac{7}{{ - 18}} + \frac{5}{6}} \right)\\ = \frac{{ - 3}}{7}.\left( {\frac{{ - 2}}{{18}} + \frac{{ - 7}}{{18}} + \frac{{15}}{{18}}} \right)\\ = \frac{{ - 3}}{7}.\frac{{ 6}}{{18}}\\ = \frac{-1}{7}\end{array}\).
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tính A = \(\frac{\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{90}}{5+\frac{5}{3}+\frac{5}{6}+\frac{1}{2}+...+\frac{1}{9}}\)
bài 1 : tính phân số:a) frac{5}{7}+frac{4}{9}?;frac{4}{5}-frac{2}{3}?;frac{9}{11}+frac{3}{8}?;frac{16}{25}-frac{2}{5}??b)5+frac{3}{5}?;10-frac{9}{16}?;frac{2}{3}-left(frac{1}{6}+frac{1}{8}right)?c)frac{5}{7}+frac{7}{6}?;frac{7}{12}+frac{17}{18}?;frac{9}{8}+frac{15}{32}?;4+frac{35}{45}?d)frac{11}{4}-frac{15}{16}?;frac{5}{6}-frac{5}{8}?;frac{196}{64}-2?;3-frac{13}{9}?e)frac{8}{5}+frac{7}{6}+frac{5}{9}-2?;3-frac{5}{6}-frac{4}{9}+frac{32}{24}?
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bài 1 : tính phân số:
a) \(\frac{5}{7}+\frac{4}{9}=?;\frac{4}{5}-\frac{2}{3}=?;\frac{9}{11}+\frac{3}{8}=?;\frac{16}{25}-\frac{2}{5}=?\)=?
b)\(5+\frac{3}{5}=?;10-\frac{9}{16}=?;\frac{2}{3}-\left(\frac{1}{6}+\frac{1}{8}\right)=?\)
c)\(\frac{5}{7}+\frac{7}{6}=?;\frac{7}{12}+\frac{17}{18}=?;\frac{9}{8}+\frac{15}{32}=?;4+\frac{35}{45}=?\)
d)\(\frac{11}{4}-\frac{15}{16}=?;\frac{5}{6}-\frac{5}{8}=?;\frac{196}{64}-2=?;3-\frac{13}{9}=?\)
e)\(\frac{8}{5}+\frac{7}{6}+\frac{5}{9}-2=?;3-\frac{5}{6}-\frac{4}{9}+\frac{32}{24}=?\)
a)\(\dfrac{5}{7}+\dfrac{4}{9}=\dfrac{45}{63}+\dfrac{28}{63}=\dfrac{73}{63}\) ; \(\dfrac{9}{11}+\dfrac{3}{8}=\dfrac{72}{88}+\dfrac{33}{88}=\dfrac{105}{88}\)
\(\dfrac{4}{5}-\dfrac{2}{3}=\dfrac{12}{15}-\dfrac{10}{15}=\dfrac{2}{15}\); \(\dfrac{16}{25}-\dfrac{2}{5}=\dfrac{16}{25}-\dfrac{10}{25}=\dfrac{6}{25}\)
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Xem thêm câu trả lời
tính bằng cách thuận tiện nhất: \(6\frac{2}{7}+7\frac{3}{5}+8\frac{6}{9}+9\frac{1}{4}+\frac{2}{5}+\frac{5}{7}+\frac{1}{3}+\frac{3}{4}\)
1 tính
a \(\left(\frac{9}{14}-\frac{9}{21}\right):\left(\frac{4}{5}+\frac{5}{6}\right)\)
b \(\frac{7}{10}-\frac{-3}{4}+\frac{-5}{6}-\frac{1}{5}+\frac{-2}{3}\)
c \(\left(-2\right)^2.\left(\frac{3}{4}-0,25\right):\left(2\frac{1}{4}-1\frac{1}{6}\right)\)
d \(-\frac{1}{7}.\left(9\frac{1}{2}-0,75\right):\frac{2}{7}+0,625:1\frac{2}{3}\)
a) 45/343
b) -1/4
c) 24/13
d) -4
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cậu làm cả các bước cho tớ thầy tớ ko có làm kết quả ko đâu
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Tính nhanh:
\(N=\frac{1}{6}.\frac{5}{9}+\frac{5}{9}.\frac{2}{7}+\frac{1}{9}.\frac{5}{7}-\frac{5}{9}.\frac{3}{7}\)
\(N=\frac{1}{6}.\frac{5}{9}+\frac{5}{9}.\frac{2}{7}+\frac{1}{9}.\frac{5}{7}-\frac{5}{9}.\frac{3}{7}\)
\(N=\frac{1}{6}.\left(\frac{5}{9}+\frac{1}{9}\right).\left(\frac{2}{7}+\frac{5}{7}-\frac{3}{7}\right)\)
\(N=\frac{1}{6}.\frac{6}{9}.\frac{4}{7}\)
\(N=\frac{1}{9}.\frac{4}{7}\)
\(N=\frac{4}{63}\)
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\(N=\frac{1}{6}.\frac{5}{9}+\frac{5}{9}.\frac{2}{7}+\frac{1}{9}.\frac{5}{7}-\frac{5}{9}.\frac{3}{7}\)
\(N=\frac{1}{6}.\frac{5}{9}+\frac{5}{9}.\frac{2}{7}+\frac{5}{9}.\frac{1}{7}-\frac{5}{9}.\frac{3}{7}\)
\(N=\frac{5}{9}.\left(\frac{1}{6}+\frac{2}{7}+\frac{1}{7}-\frac{3}{7}\right)\)
\(N=\frac{5}{9}.\frac{1}{6}\)
\(N=\frac{5}{54}\)