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a: =(5/7+2/7)+(4/3+5/3)=3+1=4
b: =(17/12+7/12)+(29/7-8/7)
=2+3=5
c: =(2/5+3/5)+(6/9+1/3)+(7/4+1/4)
=1+2+1
=4
d: =(1/3+2/3)+(13/17+4/17)+(29/11+4/11)
=1+1+3=5
1+2+3+4+5+6+7+8+9+1+2+3+4+5+6+7+8+9+1+2+3+4+5+6+7+8+9=135
1.a,=(54+45+1).113
=100.113
=11300
b,=(3/7+8/14)+(4/9+10/18)
=1+1
=2
2.a,=13/10+1/3
=49/30
b,=12/9.(1/12+1/6)
=12/9.1/4
=1/3
c,=3/4.3/2
=9/8
d,=3/2-1/3
=7/6
1:tính bằng cách thuận tiện nhất:
a)54 x 113 + 45 x 113 + 113
= 54 x 113 + 45 x 113 + 113x1
=113 x(54+45+1)
= 113x100
=1300
b)3/7 + 4/9 + 8/14 + 10/18
=(3/7+8/14)+(4/9+10/18)
= 1 + 1
=2
a)\(=\dfrac{3}{3}+\dfrac{4}{3}=\dfrac{7}{3}\)
b)\(=\dfrac{5}{9}\times\dfrac{3}{2}=\dfrac{15}{18}=\dfrac{5}{6}\)
d)\(=\left(\dfrac{12}{8}-\dfrac{3}{8}\right)\times2=\dfrac{9}{8}\times2=\dfrac{18}{8}=\dfrac{9}{4}\)
c)\(=\dfrac{4}{3}-\dfrac{5}{6}=\dfrac{8}{6}-\dfrac{5}{6}=\dfrac{3}{6}=\dfrac{1}{2}\)
a) 1 + 4/3 = 7/3
b) 5/9 : 2/3 = 5/6
c ) 4/3 -1/3 x 5/2
= 1 x 5/2
= 5/2
d) ( 3/2 - 3/8) : 1/2
= 9/8 : 1/2
= 9/4
e) 15/16 : 3/8 x 3/4
= 5/2 x 3/4
= 15/8
f) 7/19 x 1/3 x 7/19 x 2/3
= 7/19 x (1/3 x 2/3)
= 7/19 x 2/9
= 14/171
g) 3/5 x 8/27 x 25/3
= 3/5 x 25/3 x 8/27
= 5 x 8/27
= 40/27
h) 1/5 + 4/11 + 4/5 + 7/11
= (1/5 + 4/5) + (4/11 + 7/11)
= 1 + 1
= 2
1) 1/3 x 1/2 x 3/7 = 3/42 = 1/14
2) 5/4 x 1/3 +1/7 = 5/12 + 1/7 = 35/84 + 12/84 = 47/84
3) 8 x ( 8/9 - 2/3 ) = 8 x 2/9 = 16/9
4) 5/6 x 48/20 x 1/2 = 240/240 = 1
5) ( 2/5 + 3/4 ) + 8 = 23/20 + 8 = 23//20 + 160/20 = 183/20
6) 10 x ( 1/2 - 1/5 ) = 10 x 3/10 = 10/1 x 3/10 = 30/10 = 3
a) \(\frac{3}{7}+\frac{2}{5}+\frac{1}{3}=\frac{3\cdot15}{7\cdot15}+\frac{2\cdot21}{5\cdot21}+\frac{1\cdot35}{3\cdot35}\)
\(=\frac{45}{105}+\frac{42}{105}+\frac{35}{105}=\frac{45+42+35}{105}=\frac{122}{105}\)
b) \(6-\left(\frac{3}{4}+\frac{2}{7}\right)=6-\left(\frac{21}{28}+\frac{8}{28}\right)=6-\frac{29}{28}=\frac{139}{26}\)
c) \(\frac{8}{9}-\frac{3}{7}:\frac{2}{9}\cdot\frac{3}{4}=\frac{8}{9}-\frac{27}{14}\cdot\frac{3}{4}=\frac{8}{9}-\frac{81}{56}=-\frac{281}{504}\)
hok tốt
.....
\(\frac{3}{7}+\frac{2}{5}+\frac{1}{3}\)
\(=\frac{29}{35}+\frac{1}{3}\)
\(=\frac{122}{105}\)
\(6-\left(\frac{3}{4}+\frac{2}{7}\right)\)
\(=6-\frac{29}{28}\)
\(=\frac{139}{28}\)
\(\frac{8}{9}-\frac{3}{7}\div\frac{2}{9}\times\frac{3}{4}\)
\(=\frac{8}{9}-\frac{27}{14}\times\frac{3}{4}\)
\(=\frac{8}{9}-\frac{81}{56}\)
\(=-\frac{281}{504}\)