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a) Cách 1 : (3/4 + 1/2) x 5/7
= 5/4 x 5/7
= 25/28
Cách 2 : (3/4 + 1/2) x 5/7
= 3/4 x 5/7 + 1/2 x 5/7
= 15/28 + 5/14
= 25/28
b) Cách 1 : 5/7 x 13/21 + 2/7 x 13/21
= 65/147 + 26/147
= 13/21
Cách 2 : 5/7 x 13/21 + 2/7 x 13/21
= (5/7 + 2/7) x 13/21
= 1 x 13/21
= 13/21
câu c tự làm
a; 60 \(\times\) (\(\dfrac{7}{12}\) + \(\dfrac{4}{15}\))
= 60 \(\times\) \(\dfrac{7}{12}\) + 60 \(\times\) \(\dfrac{4}{15}\)
= 35 + 16
= 51
a,\(60\times\left(\frac{7}{12}+\frac{4}{15}\right)\)\(=\frac{60\times7}{12}+\frac{60\times4}{15}\)
\(=\frac{12\times5\times7}{12}+\frac{15\times4\times4}{15}\)
\(=5\times7+4\times4\)
\(=35+16\)
\(=51\)
b, \(\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times...\times\frac{8}{9}\)\(=\frac{1\times2\times3\times4\times5\times6\times7\times8}{2\times3\times4\times5\times6\times7\times8\times9}\)
\(=\frac{1}{9}\)
a) 6/7 - 3/6 = 21/42 - 21/42 = 15/42
b) 2/5 x 4/7 = 8/35
c) 3/10 : 6/10 = 3/10 x 10/6 = 1/2
d) 5/9 + 3/4 = 32/36 = 8/9
e) 1/3 : 6 = 1/3 x 1/6 = 1/18
g) 3 x 2/5 = 6/5
h) 6/7 + 4/21 = 22/21
k cho mk nhé!
\(1.\)
\(x\div\frac{4}{3}=\frac{3}{7}+\frac{2}{5}\)
\(x\div\frac{4}{3}=\frac{29}{35}\)
\(x=\frac{29}{35}\times\frac{4}{3}\)
\(x=\frac{116}{105}\)
\(2.\)
\(\frac{2}{5}\times\frac{3}{6}+\frac{7}{5}\div\frac{3}{5}\)
\(=\frac{1}{5}+\frac{7}{5}\times\frac{5}{3}\)
\(=\frac{1}{5}+\frac{7}{3}\)
\(=\frac{3}{15}+\frac{35}{15}\)
\(=\frac{38}{15}\)
a,Cách 1: (6/11 + 5/11 ) x 3/7 Cách 2 :(6/11 + 5/11) x 3/7
= 1 x 3/7 =6/11 x 3/7 + 5/11 x 3/7
= 3/7 = 18/77 + 15/77
= 3/7
b, Cách 1:3/5 x 7/9 - 3/5 x 2/9 Cách 2 :3/5 x 7/9 - 3/5 x 2/9
= 7/15 - 2/15 = 3/5 x (7/9 - 2/9 )
= 1/3 = 3/5 x 5/9
= 1/3
c, Cách 1:(6/7 - 4/7) : 2/5 Cách 2: ( 6/7- 4/7 ) : 2/5
= 2/7 : 2/5 = 6/7 : 2/5 - 4/7 : 2/5
= 5/7 = 15/7 - 10/7
= 5/7
d,Cách 1:8/15 : 2/11 + 7/15 : 2/11 Cách 2:8/15 : 2/11 +7/15 : 2/11
= 88/30 + 77/30 =(8/15+7/15) :2/11
= 11/2 = 1 : 2/11
= 11/2
Bài 2 cậu tự làm nhé !
\(a,\dfrac{4}{15}:\dfrac{4}{7}< x< \dfrac{2}{5}\times\dfrac{10}{3}\\ \Leftrightarrow\dfrac{7}{15}< x< \dfrac{4}{3}\\ \Leftrightarrow x=1\)
\(b,\dfrac{3}{5}\times\dfrac{3}{7}+\dfrac{2}{5}\times\dfrac{4}{7}=\dfrac{9}{35}+\dfrac{8}{35}=\dfrac{17}{35}\)