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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: \(\dfrac{4}{7}\cdot\dfrac{2}{13}+\dfrac{8}{13}:\dfrac{7}{4}+\dfrac{4}{7}:\dfrac{13}{2}+\dfrac{4}{7}\cdot\dfrac{1}{13}\)
\(=\dfrac{4}{7}\left(\dfrac{2}{13}+\dfrac{8}{13}+\dfrac{2}{13}+\dfrac{1}{13}\right)\)
\(=\dfrac{4}{7}\)
\(\dfrac{7}{8}\) \(\times\) \(\dfrac{1}{6}\) + \(\dfrac{7}{8}\) \(\times\) \(\dfrac{2}{6}\) + \(\dfrac{7}{8}\) \(\times\) \(\dfrac{1}{2}\)
= \(\dfrac{7}{8}\) \(\times\) ( \(\dfrac{1}{6}\) + \(\dfrac{2}{6}\) + \(\dfrac{1}{2}\) )
= \(\dfrac{7}{8}\) \(\times\) ( \(\dfrac{3}{6}\) + \(\dfrac{1}{2}\))
= \(\dfrac{7}{8}\) \(\times\) ( \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\))
= \(\dfrac{7}{8}\) \(\times\) 1
= \(\dfrac{7}{8}\)
25 \(\times\) 5 \(\times\) 4 \(\times\)2 - 176
= (25 \(\times\) 4 ) \(\times\) ( 5 \(\times\) 2) - 176
= 100 \(\times\) 10 - 176
= 1000 - 176
= 824
\(\dfrac{7}{8}\times\dfrac{1}{6}+\dfrac{7}{8}\times\dfrac{2}{6}+\dfrac{7}{8}\times\dfrac{1}{2}\)
\(=\dfrac{7}{8}\times\left(\dfrac{1}{6}+\dfrac{2}{6}+\dfrac{1}{2}\right)\)
\(=\dfrac{7}{8}\times1\)
\(=\dfrac{7}{8}\)
__________________________
\(25\times5\times4\times2-176\)
\(=\left(25\times4\right)\times\left(4\times2\right)-176\)
\(=1000-176\)
\(=824\)
Chúc bạn học tốt
a: \(=\dfrac{48-45}{54}\cdot\dfrac{9}{4}=\dfrac{3}{54}\cdot\dfrac{9}{4}=\dfrac{27}{216}=\dfrac{1}{8}\)
b: \(=\dfrac{6}{5}+1=\dfrac{11}{5}\)
c: \(=\dfrac{7\cdot28\cdot15}{9\cdot25\cdot14}=\dfrac{1}{2}\cdot\dfrac{28}{25}\cdot\dfrac{5}{3}=\dfrac{140}{150}=\dfrac{14}{15}\)
tính bằng cách thuận tiện nhất
a,4/15 x 7/8 + 4/15 x 2/9
b, 13/29 x 23/11 -13/19 x 8/11 - 13/19 x 4/11
Hướng dẫn giải:
a) 71 x 5 x 4 = 71 x (5 x 4) = 71 x 20 = 1420
b) 123 x 50 x 2 = 123 x (50 x 2) = 123 x 100 = 12300
c) 4 x 138 x 25 = (4 x 25) x 138 = 100 x 138 = 13800
d) 25 x 96 x 4 = (25 x 4) x 96 = 100 x 96 = 9600
e) 5 x 81 x 2 = (5 x 2) x 81 = 10 x 81 = 810
g) 50 x 104 x 2 = (50 x 2) x 104 = 100 x 104 = 10400
Bài 2: Tính bằng cách thuận tiện nhất
\(\text{a. 1255 + 436 + 145}\)
\(=\left(1255+145\right)+436\)
\(=1400+436\)
\(=1836\)
\(\text{b. 142 x 12 + 142 x 18}\)
\(=142\times\left(12+18\right)\)
\(=142\times30\)
\(=4260\)
\(\text{c. 4 x 18 x 25}\)
\(=\left(25\times4\right)\times18\)
\(=100\times18\)
\(=1800\)
Bài 2:
a: \(=1400+436=1836\)
b: =142(12+18)
=142*30
=4260
c: \(=100\cdot18=1800\)
Bài 3:
a: \(41m^219dm^2>409dm^2\)
b: \(90000cm^2< 90m^2\)
c: \(30m^26dm^2< 3060dm^2\)
d: \(8012cm^2>8dm^212cm^2\)
e: \(5dm^29cm^2=509cm^2\)
f: \(3940dm^2=39m^240dm^2\)
g: \(300m^26dm^2>3006dm^2\)
h: \(2009cm^2< 21dm^2\)
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,\(26\times\frac{13}{42}\div13\)
\(=\left(26\div13\right)\times\frac{13}{42}\)
\(=2\times\frac{13}{42}\)
\(=\frac{13}{21}\)
a) 4x7x5
=(4x5)x7
=20x7
=140
b) 15x9x2
=(15x2)x9
=30x9
=270
c) 25x895x4
=(25x4)x895
=100x895
=89500
d) 2x3238x50
=(2x50)x3238
=100x3238
=323800
tk nhé
ui avatra idol tui