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1) Ta có: \(\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{7}{25}\cdot\dfrac{5}{7}\right)\)
\(=\left(\dfrac{3}{4}\cdot\dfrac{5}{97}+\dfrac{1}{9}\cdot\dfrac{13}{47}\right)\cdot\left(\dfrac{1}{5}-\dfrac{1}{5}\right)\)
=0
2) Ta có: \(\dfrac{8}{17}\cdot\dfrac{4}{15}+\dfrac{8}{17}\cdot\dfrac{22}{15}-\dfrac{8}{15}\cdot\dfrac{9}{17}\)
\(=\dfrac{8}{17}\left(\dfrac{4}{15}+\dfrac{22}{15}-\dfrac{9}{15}\right)\)
\(=\dfrac{8}{17}\cdot\dfrac{15}{15}=\dfrac{8}{17}\)
3) Ta có: \(\dfrac{2021}{2}\cdot\dfrac{1}{3}+\dfrac{4042}{4}\cdot\dfrac{1}{5}+\dfrac{6063}{3}\cdot\dfrac{22}{15}\)
\(=\dfrac{2021}{2}\left(\dfrac{1}{3}+\dfrac{1}{5}\right)+2021\cdot\dfrac{22}{15}\)
\(=\dfrac{2021}{2}\cdot\dfrac{8}{15}+\dfrac{2021}{2}\cdot\dfrac{44}{15}\)
\(=\dfrac{2021}{2}\cdot\dfrac{52}{15}\)
\(=\dfrac{52546}{15}\)
4) Ta có: \(\dfrac{4}{7}\cdot\dfrac{2}{13}+\dfrac{8}{13}:\dfrac{7}{4}+\dfrac{4}{7}:\dfrac{13}{2}+\dfrac{4}{7}\cdot\dfrac{1}{13}\)
\(=\dfrac{4}{7}\left(\dfrac{2}{13}+\dfrac{8}{13}+\dfrac{2}{13}+\dfrac{1}{13}\right)\)
\(=\dfrac{4}{7}\)
\(=\dfrac{4}{15}x\left(13+4-2\right)=\dfrac{4x15}{15}=4\)
a,\(\frac{1}{5}\times\frac{2}{9}\div\frac{1}{15}\)
\(=\frac{1}{5}\times\frac{2}{9}\times15\)
\(=\left(\frac{1}{5}\times15\right)\times\frac{2}{9}\)
\(=3\times\frac{2}{9}\)
\(=\frac{2}{3}\)
b\(\frac{4}{15}\times\frac{7}{15}\times\frac{5}{4}\)
\(=\left(\frac{4}{15}\times\frac{5}{4}\right)\times\frac{7}{15}\)
\(=\frac{1}{3}\times\frac{7}{15}\)
\(=\frac{7}{45}\)
c,\(\frac{21}{23}\times\frac{5}{11}\times\frac{44}{?}\)
d,\(26\times\frac{13}{42}\div13\)
\(=\left(26\div13\right)\times\frac{13}{42}\)
\(=2\times\frac{13}{42}\)
\(=\frac{13}{21}\)
X : 1/2 = 2/3 x 4/5 x 3/4 x 15/8
X : 1/2 = ( 2/3 x 3/4) x (4/5 x 15/8)
X :1/2 = 1/2 x 3/2
X :1/2 = 3/4
X = 3/4 x 1/2
X. = 3/8
Tk ung ho mk nha!!!
x:1/2=2/3*4/5*3/4*15/8
x*2=3/4
x=3/4:2
x=3/8
nho k cho minh voi nha
a) \(\dfrac{2}{9}+\dfrac{3}{5}-\dfrac{1}{15}=\dfrac{37}{45}-\dfrac{1}{15}=\dfrac{37}{45}-\dfrac{3}{45}=\dfrac{34}{45}\)
b) \(\dfrac{5}{12}\times\dfrac{4}{5}\div4=\dfrac{1}{3}\div4=\dfrac{1}{12}\)
c) \(\dfrac{8}{9}-\dfrac{4}{15}\div\dfrac{2}{5}=\dfrac{8}{9}-\dfrac{2}{3}=\dfrac{8}{9}-\dfrac{6}{9}=\dfrac{2}{9}\)
4/15 + 1/2
= 8/30 + 15/30
= 23/30
51/9 - 2/3
= 51/9 - 6/9
= 45/9
= 5
3/4 × 15/26
= 45/104
7/3 : 5/14
= 7/3 × 14/5
= 98/15
`3xx4/15+2xx4/15-5xx4/15`
`=4/15xx(3+2-5)`
`=4/15xx0`
`=0`
`3 xx 4/15 + 2 xx 4/15 - 5 xx 4/15`
`= 4/15 xx (3 + 2 - 5)`
`= 4/15 xx 0`
`= 0`