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Dãy đó có số số hạng là
\(\left(\frac{8}{9}-\frac{1}{9}\right)\div\frac{1}{9}+1=\)\(8\)
Tổng dãy đó là
\(\left(\frac{1}{9}+\frac{8}{9}\right)\times8\div2=4\)
Đáp số : 4
\(\frac{1}{9}+\frac{2}{9}+\frac{3}{9}+.....+\frac{7}{9}+\frac{8}{9}\)
= \(\frac{1+2+3+4+5+6+7+8}{9}\)
= \(\frac{36}{9}=4\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\frac{11}{15}+\frac{5}{7}+\frac{2}{7}+\frac{4}{15}=\left(\frac{11}{15}+\frac{4}{15}\right)+\left(\frac{5}{7}+\frac{2}{7}\right)\)
\(=2\)
b) \(\frac{5}{9}\times\frac{1}{2}\times\frac{5}{9}\times\frac{6}{4}=\frac{25}{81}\times\frac{3}{4}=\frac{25}{108}\)
c) \(\frac{7}{8}\div\frac{1}{2}+\frac{9}{8}\div\frac{1}{2}=\left(\frac{7}{8}+\frac{9}{8}\right)\div\frac{1}{2}\)
\(=2\div\frac{1}{2}=4\)
d) \(\frac{17}{10}+\frac{1}{2}-\frac{7}{10}=\left(\frac{17}{10}-\frac{7}{10}\right)+\frac{1}{2}\)
\(=1+\frac{1}{2}=\frac{3}{2}\)
a) \(\frac{11}{15}+\frac{5}{7}+\frac{2}{7}+\frac{4}{15}\)
\(=\left(\frac{11}{15}+\frac{4}{15}\right)+\left(\frac{5}{7}+\frac{2}{7}\right)\)
\(=1+1\)
\(=2\)
b) \(\frac{5}{9}.\frac{1}{2}.\frac{5}{9}.\frac{6}{4}\)
\(=\left(\frac{5}{9}\right)^2\left(\frac{1}{2}.\frac{6}{4}\right)\)
\(=\frac{25}{81}.\frac{3}{4}\)
\(=\frac{25}{108}\)
c) \(\frac{7}{8}:\frac{1}{2}+\frac{9}{8}:\frac{1}{2}\)
\(=\frac{7}{8}.2+\frac{9}{8}.2\)
\(=2\left(\frac{7}{8}+\frac{9}{8}\right)\)
\(=2.\frac{16}{8}\)
\(=2.2\)
\(=4\)
d) \(\frac{17}{10}+\frac{1}{2}-\frac{7}{10}\)
\(=\left(\frac{17}{10}-\frac{7}{10}\right)+\frac{1}{2}\)
\(=1+\frac{1}{2}\)
\(=\frac{2}{2}+\frac{1}{2}\)
\(=\frac{3}{2}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a,(11/15+4/15)+(5/7+2/7)
=1+1
=2
b,5/9x(1/2+6/4)
=5/9x2
=10/9
c,1/2:(7/8+9/8)
=1/2:2
=1
d,(17/10-7/10)+1/2
=1+1/2
=3/2
![](https://rs.olm.vn/images/avt/0.png?1311)
a)\(\frac{77}{24}\)=\(3\frac{5}{24}\)
b)=10
c)\(\frac{24}{35}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{6}{8}+\frac{4}{8}=\frac{6+4}{8}=\frac{10}{8}=\frac{5}{4}\)
\(\frac{5}{7}-\frac{1}{7}=\frac{5-1}{7}=\frac{4}{7}\)
\(\frac{9}{6}+\frac{4}{8}=\frac{9\times3}{6\times3}+\frac{4\times2}{8\times2}=\frac{27}{19}+\frac{8}{19}=\frac{35}{19}\)
\(\frac{5}{7}-\frac{4}{6}=\frac{5\times6}{7\times6}-\frac{4\times7}{6\times7}=\frac{30}{42}-\frac{28}{42}=\frac{2}{42}=\frac{1}{21}\)
\(\frac{6}{8}+\frac{4}{8}=\frac{6+4}{8}=\frac{10}{8}=\frac{5}{4}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
b) \(\frac{5}{9}\)và \(\frac{5}{8}\) :Quy đồng mẫu số : \(\frac{5}{9}\) = \(\frac{5.8}{9.8}\) = \(\frac{40}{72}\) ; \(\frac{5}{8}\) = \(\frac{5.9}{8.9}\) = \(\frac{45}{72}\)
Vì \(\frac{40}{72}\) < \(\frac{45}{72}\) nên \(\frac{5}{9}\) < \(\frac{5}{8}\)
c)\(\frac{8}{7}\) và \(\frac{7}{8}\) :Quy đồng mẫu số: \(\frac{8}{7}\) = \(\frac{8.8}{7.8}\) = \(\frac{64}{56}\) ; \(\frac{7}{8}\) = \(\frac{7.7}{8.7}\) =\(\frac{49}{56}\)
Vì \(\frac{64}{56}\) > \(\frac{49}{56}\) nên \(\frac{8}{7}\) > \(\frac{7}{8}\)
bạn an đông à cái câu A của bạn sai một chút.
CHÚC BẠN HỌC TỐT !
a)\(\frac{3}{7}\) và\(\frac{2}{8}\) :Quy đồng mẫu số : \(\frac{3}{7}\) = \(\frac{3.8}{7.8}\) = \(\frac{24}{56}\) ; \(\frac{2}{8}\) = \(\frac{2.7}{8.7}\) = \(\frac{14}{56}\)
Vì \(\frac{24}{56}\) > \(\frac{14}{56}\) nên \(\frac{3}{7}\) > \(\frac{2}{8}\)
\(q-\frac{7}{9}=\frac{1}{8}\)
\(q=\frac{1}{8}+\frac{7}{9}\)
\(q=\frac{65}{72}\)