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a) \(\frac{11}{15}+\frac{5}{7}+\frac{2}{7}+\frac{4}{15}\)
\(=\left(\frac{11}{15}+\frac{4}{15}\right)+\left(\frac{5}{7}+\frac{2}{7}\right)\)
\(=\frac{15}{15}+\frac{7}{7}\)
\(=1+1\)
\(=2\)
b) \(\frac{17}{10}+\frac{1}{2}-\frac{7}{10}\)
\(=\left(\frac{17}{10}-\frac{7}{10}\right)+\frac{1}{2}\)
\(=1+\frac{1}{2}\)
\(=\frac{2}{2}+\frac{1}{2}\)
\(=\frac{3}{2}\)
\(x:\frac{2}{7}=\frac{2}{3}\)
\(x=\frac{2}{3}.\frac{2}{7}\)
\(x=\frac{4}{21}\)
\(\frac{11}{10}-\frac{2}{5}:\frac{2}{3}\)
\(=\frac{11}{10}-\frac{3}{5}\)
\(=\frac{1}{2}\)
1/2 + 3/6 + 5/10 + 7/14 + 9/18 + 11/22
= 1/2 + ( 3/6=1/2) + (5/10=1/2) + (7/14 = 1/2) +( 9/18 =1/2) + (11/22 = 1/2)
= 1/2 + 1/2 + 1/2 + 1/2 + 1/2 + 1/2
= 1 + 1 + 1
= 3
\(\frac{1}{2}+\frac{3}{6}+\frac{5}{10}+\frac{7}{14}+\frac{9}{18}+\frac{11}{22}=\frac{1}{2}+\frac{1}{2}+\frac{1}{2}+\frac{1}{2}+\frac{1}{2}+\frac{1}{2}=\frac{1}{2}.6=\frac{6}{2}=3\)
3/4+1/2+5/8=15/8
5/9+9/8-15/28=577/504
11/30-9/25x15/27=1/6
3/4:5/8:3/10=4
a) 2/5 + 1/2 + 7/10
= 4/10 + 5/10 + 7/10
= 9/10 + 7/10
= 16/10 = 8/5
b) 4/9 + 11/8 - 5/6
= 32/72 + 99/72 - 60/72
= 191/72
c) 9/20 - 8/15 x 5/12
= 9/20 - 2/9
= 41/180
d) 2/3 : 4/5 : 7/12
= 5/6 : 7/12
= 10/7
1-2+3-4+5-6+7-8+9-10+11=(-1)+(-1)+(-1)...+(-1)+11
=(-1).5+11
=(-5)+11
=6
\(\frac{10}{11}:\left(\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}\right)\)
\(=\frac{10}{11}:\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}\right)\)
\(=\frac{10}{11}:\left(\frac{1}{3}-\frac{1}{11}\right)\)
\(=\frac{10}{11}:\frac{8}{33}=\frac{10}{11}.\frac{33}{8}\)
\(=\frac{15}{4}\)
Trả lời:
\(\frac{10}{11}\div\left(\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}\right)\)
\(=\frac{10}{11}\div\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}\right)\)
\(=\frac{10}{11}\div\left(\frac{1}{3}-\frac{1}{11}\right)\)
\(=\frac{10}{11}\div\frac{8}{33}\)
\(=\frac{10}{11}\times\frac{33}{8}\)
\(=\frac{15}{4}\)
