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\(\dfrac{8}{9}+\dfrac{3}{18}=\dfrac{16}{18}+\dfrac{3}{18}=\dfrac{19}{18}\) \(\dfrac{5}{7}-\dfrac{4}{11}=\dfrac{55}{77}-\dfrac{28}{77}=\dfrac{3}{11}\)
\(\dfrac{3}{4}+\dfrac{4}{5}=\dfrac{15}{20}+\dfrac{16}{20}=\dfrac{21}{20}\) \(\dfrac{5}{7}-\dfrac{3}{5}=\dfrac{25}{35}-\dfrac{21}{35}=\dfrac{4}{35}\)
\(\dfrac{7}{9}X\dfrac{3}{4}=\dfrac{7}{9}X\dfrac{3}{4}=\dfrac{7}{12}\) \(\dfrac{8}{3}X\dfrac{21}{4}=\dfrac{8}{3}X\dfrac{21}{4}=14\)
\(\dfrac{12}{7}:\dfrac{1}{4}=\dfrac{12}{7}X\dfrac{4}{1}=\dfrac{48}{7}\) \(\dfrac{7}{2}:\dfrac{9}{4}=\dfrac{7}{2}X\dfrac{4}{9}=\dfrac{14}{9}\)
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2/3 + 3/4=17/12
9/4 + 3/5=57/20
5/24 + 1/4=11/24
3/15 - 5/35=2/35 18/27 - 2/6=1/3 37/12 - 3=1/12
11/9 x 3/22=1/6 7/13 x 13/7=1 4 x6/7=24/7
2/5 : 3/10=4/3 3/8 : 9/4=1/6 8/21 : 4/7=2/3
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2/5 + 11/15 = 17/15
7/8 - 7/9 = 7/72
11/13 x 26/31 = 22/31
16/24 : 4 = 1/6
30 : 6/5 = 25
9/16 : 4 = 9/64
1/2 : 1/3 x 8/15 = 3/2 x 8/15 = 4/5
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a) 32x31+69x31-31
=992+2070
=3062
b) 43x166+14x83
=7138+1162
=8300
c) 7/2-3/2:x=5/4
3/2:x=7/2-5/4
3/2:x= 9/4
x=3/2:9/4
x= 2/3
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(dấu chấm là dấu nhân nha e)
*\(\dfrac{1}{2}\). \(\dfrac{1}{4}\)+\(\dfrac{3}{4}\)
= \(\dfrac{1}{8}\)+\(\dfrac{3}{4}\)
= \(\dfrac{1}{8}\)+\(\dfrac{6}{8}\)= \(\dfrac{7}{8}\)
*\(\dfrac{3}{4}\).\(\dfrac{5}{6}\).\(\dfrac{8}{15}\)
= \(\left(\dfrac{3}{4}.\dfrac{8}{15}\right)\).\(\dfrac{5}{6}\)
= \(\dfrac{2}{5}\).\(\dfrac{5}{6}\)
= \(\dfrac{1}{3}\)
*\(\dfrac{12}{19}\): \(\dfrac{17}{38}\).\(\dfrac{16}{9}\)
= \(\dfrac{12}{19}\). \(\dfrac{38}{17}\).\(\dfrac{16}{9}\)= 2,5
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a) \(\frac{1}{4}+\frac{2}{5}+\frac{6}{8}+\frac{9}{15}+\frac{8}{1}\)
\(=\left(\frac{1}{4}+\frac{6}{8}\right)+\left(\frac{2}{5}+\frac{9}{15}\right)+\frac{8}{1}\)
\(=\left(\frac{1}{4}+\frac{3}{4}\right)+\left(\frac{2}{5}+\frac{3}{5}\right)+\frac{8}{1}\)
\(=\frac{4}{4}+\frac{5}{5}+\frac{8}{1}\)
\(=1+1+8\)
\(=10\)
b) \(\frac{15}{31}\cdot\frac{16}{43}+\frac{15}{31}\cdot\frac{27}{43}\)
\(=\frac{15}{31}\cdot\left(\frac{16}{43}+\frac{27}{43}\right)\)
\(=\frac{15}{31}\cdot\frac{43}{43}\)
\(=\frac{15}{31}\cdot1=\frac{15}{31}\)
**** !
\(\frac{2}{5}+1=\frac{2}{5}+\frac{5}{5}=\frac{7}{5}\) ;\(\frac{6}{7}.4=\frac{24}{7}\);\(\frac{3}{7}:2=\frac{3}{7}.\frac{1}{2}=\frac{3}{14}\);\(2:\frac{2}{4}=2.\frac{4}{2}=2.2=4\);\(\frac{3}{4}.4+\frac{1}{3}=\frac{12}{4}+\frac{1}{3}=3+\frac{1}{3}=\frac{10}{3}\);\(\frac{1}{4}:\frac{1}{3}-\frac{1}{2}=\frac{1}{4}.\frac{3}{1}-\frac{1}{2}=\frac{3}{4}-\frac{1}{2}=\frac{1}{4}\)
\(\frac{2}{5}+1=\frac{2}{5}+\frac{5}{5}=\frac{7}{5}\)
\(\frac{6}{7}\times4=\frac{6\times4}{7}=\frac{24}{7}\)
\(\frac{3}{7}\div2=\frac{3}{7}\times\frac{1}{2}=\frac{3\times1}{7\times2}=\frac{3}{14}\)
\(2\div\frac{2}{4}=2\times\frac{4}{2}=2\times2=4\)
\(\frac{3}{4}\times4+\frac{1}{3}=\frac{3\times4}{4}+\frac{1}{3}=3+\frac{1}{3}=\frac{9}{3}+\frac{1}{3}=\frac{10}{3}\)
\(\frac{1}{4}\div\frac{1}{3}-\frac{1}{2}=\frac{1}{4}\times3-\frac{1}{2}=\frac{1\times3}{4}-\frac{1}{2}=\frac{3}{4}-\frac{1}{2}=\frac{3}{4}-\frac{2}{4}=\frac{1}{4}\)