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\(a.60\times\left(\frac{7}{12}+\frac{4}{15}\right)\)
\(=60\times\left(\frac{35}{60}+\frac{16}{60}\right)\)
\(=60\times\frac{51}{60}\)
\(=51\)
\(b.\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times\frac{5}{6}\times\frac{6}{7}\times\frac{7}{8}\times\frac{8}{9}\)
\(=\frac{1\times2\times3\times4\times5\times6\times7\times8}{2\times3\times4\times5\times6\times7\times8\times9}\)
\(=\frac{1}{9}\)
\(\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times\frac{5}{6}\)
\(=\frac{2\times3\times4\times5}{3\times4\times5\times6}\)
\(=\frac{2}{6}\)
\(=\frac{1}{3}\)
a, 2x9x5x7x4x25
=2x5x4x25x9x7
=10x100x63
=63000
b,6x14x5x25x3x4
=6x5x3x4x25x14
=90x100x14
=9000x14
=126000
~HT~
a, 2.9.5.7.4.25=(2.5).(25.4).(7.9)
=10.100.63=63000
câu b làm tương tự tích giúp mình nha
= 4/5 x ( 3/7 + 6/7 - 4/14 )
= 4/5 x ( 3/7 + 6/7 - 2/7 )
= 4/5 x 7/7
= 4/5
TL:
8/15 x 5/6 = 40/90 = 4/9
41/20 x 3/4 = 123/80
(11/23 + 9/23) + (18/23 + 2/23) = 20/23 + 20/23 = 40/43
HT
\(\left(\frac{2}{3}\times\frac{4}{5}\right)\times\frac{5}{6}\) = \(\frac{2}{3}\times\frac{4}{5}\times\frac{5}{6}\)=\(\frac{2\times4\times5}{3\times5\times6}\)=\(\frac{2\times4\times5}{3\times5\times2\times3}\)=\(\frac{4}{9}\)
\(\frac{11}{23}+\frac{2}{23}+\frac{9}{23}+\frac{18}{23}\)=\(\frac{\left(11+9\right)+\left(18+2\right)}{23}\)=\(\frac{20+20}{23}\)=\(\frac{40}{23}\)
\(\frac{27}{12}+\frac{17}{6}-\frac{25}{36}-\frac{15}{6}\)=\(\left(\frac{27}{12}-\frac{25}{36}\right)+\left(\frac{17}{6}-\frac{15}{6}\right)\)=\(\frac{14}{9}+\frac{2}{6}\)=\(\frac{17}{9}\)
/HT\
\(\Rightarrow x\times\left(\dfrac{9}{5}+\dfrac{6}{5}\right)=\dfrac{3}{4}\\ \Rightarrow x\times3=\dfrac{3}{4}\\ \Rightarrow x=\dfrac{3}{4}:3\\ \Rightarrow x=\dfrac{3}{4}\times\dfrac{1}{3}=\dfrac{1}{4}\)
\(\dfrac{9}{5}\times x+\dfrac{6}{5}\times x=\dfrac{3}{4}\)
\(x\times\left(\dfrac{9}{5}+\dfrac{6}{5}\right)=\dfrac{3}{4}\)
\(x\times3=\dfrac{3}{4}\)
\(x=\dfrac{3}{4}:3=\dfrac{3}{4}\times\dfrac{1}{3}\)
\(x=4\)