Tính:
7/12 x 3/7 + 7/12 x 4/7
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1) = \(\frac{3}{5}\)
2) =\(\frac{6}{7}\)
3)\(\frac{9}{13}\)
4)\(\frac{4}{13}\)
a] 4/12 ; 5/12 ; 11/2 ; 1/4
b] 1 ; 9/12; 12/5 ; 11/3
c] 8/21; 6/11;8/7
d] 2/3 ;2/7 15/2
a]1/3 5/12 11/2 1/4
b]1 3/4 12/5 33/9
c]8/21 6/11 8/7
d]2/3 2/7 15/2
Bài 1:
a: -8/12<0<-3/-4
b: -56/24<0<7/3
c: 4/25<1<15/13
=>-4/25>-15/13
Bài 2:
a: =-60/45=-4/3
b: =4/15-3/2-8/5=8/30-45/30-48/30=-85/30=-17/6
\(\frac{4}{7}.\frac{5}{12}+\frac{4}{7}.\frac{7}{12}+\frac{4}{7}\)
\(=\frac{4}{7}.\left(\frac{5}{12}+\frac{7}{12}+1\right)\)
\(=\frac{4}{7}\left(\frac{12}{12}+1\right)\)
\(=\frac{4}{7}.2\)
\(=\frac{8}{7}\)
\(=\dfrac{11}{12}\left(\dfrac{2}{7}+\dfrac{4}{7}+\dfrac{1}{7}\right)=\dfrac{11}{12}\cdot1=\dfrac{11}{12}\)
6 x 4 = 24 12 : 6 = 2 7 x 3 = 21 63 : 7 = 9
7 x 5 = 35 42 : 7 = 6 6 x 8 = 48 48 : 6 = 8
6 x 6 = 36 28 : 7 = 4 7 x 8 = 56 49 : 7 = 7
6 x 4 = 24 12 : 6 = 02 7 x 3 = 21 63 : 7 = 09 7 x 5 = 35 42 : 7 = 06
6 x 8 = 48 48 :6 = 8 6 x 6 = 36 28 : 7 = 04 7 x 8 = 56 49 : 7 = 07
Ta có:
\(\frac{4}{3\times7}+\frac{5}{7\times12}+\frac{1}{12\times13}+\frac{7}{13\times20}+\frac{3}{20\times23}\)
=>\(\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{12}+\frac{1}{12}-\frac{1}{13}+\frac{1}{13}-\frac{1}{20}+\frac{1}{20}-\frac{1}{23}\)
=>\(\frac{1}{3}-\frac{1}{23}=\frac{20}{69}\)
Chúc bạn học tốt !!!
Bài 1:
a: \(x=\dfrac{2}{3}:\dfrac{3}{5}=\dfrac{2}{3}\cdot\dfrac{5}{3}=\dfrac{10}{9}\)
b: \(x=\dfrac{17}{8}:\dfrac{7}{17}=\dfrac{17}{8}\cdot\dfrac{17}{7}=\dfrac{289}{56}\)
c: \(x=-\dfrac{3}{4}:\dfrac{7}{12}=\dfrac{-3}{4}\cdot\dfrac{12}{7}=\dfrac{-63}{28}=-\dfrac{9}{4}\)
d: \(\Leftrightarrow x\cdot\dfrac{1}{6}=\dfrac{3}{8}-\dfrac{1}{4}=\dfrac{1}{4}\)
hay \(x=\dfrac{1}{4}:\dfrac{1}{6}=\dfrac{3}{2}\)
e: \(\Leftrightarrow\dfrac{1}{2}:x=-4-\dfrac{1}{3}=-\dfrac{17}{3}\)
hay \(x=-\dfrac{1}{2}:\dfrac{17}{3}=\dfrac{-3}{34}\)
\(=\dfrac{7}{12}\times\left(\dfrac{3}{7}+\dfrac{4}{7}\right)=\dfrac{7}{12}\times\dfrac{7}{7}=\dfrac{7}{12}\)
`7/12xx3/7+7/12xx4/7=7/12xx(3/7+4/7)=7/12xx7/7=7/12`