Tính bằng cách thuận tiện
a) 4/9 x 7/5 : 7/9 b) 3/4 x 3/2 + 3/4 x 1/2
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a.\(\dfrac{2}{3}\times\dfrac{4}{9}+\dfrac{2}{3}\times\dfrac{5}{9}=\dfrac{2}{3}\times\left(\dfrac{4}{9}+\dfrac{5}{9}\right)=\dfrac{2}{3}\times1=\dfrac{2}{3}\)
b.\(\dfrac{7}{5}\times\dfrac{3}{4}-\dfrac{1}{2}\times\dfrac{3}{4}=\dfrac{3}{4}\times\left(\dfrac{7}{5}-\dfrac{1}{2}\right)=\dfrac{3}{4}\times\dfrac{9}{10}=\dfrac{27}{40}\)
c.\(\left(\dfrac{5}{6}+\dfrac{5}{8}\right)\times\dfrac{2}{3}=\dfrac{35}{24}\times\dfrac{2}{3}=\dfrac{35}{36}\)
a) 2/3 x 4/9 + 2/3 x 5/9
=2/3 x ( 4/9 + 5/9)
= 2/3 x 1
= 2/3
b, 7/5 x 3/4 - 1/2 x 3/4
= ( 7/5 - 1/2 ) x 3/4
= 9/10 x 3/4
= 21/40
c, ( 5/6 + 5/8 ) x 2/3
= 35/24 x 2/3
= 35/36
\(a.60\times\left(\frac{7}{12}+\frac{4}{15}\right)\)
\(=60\times\left(\frac{35}{60}+\frac{16}{60}\right)\)
\(=60\times\frac{51}{60}\)
\(=51\)
\(b.\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times\frac{5}{6}\times\frac{6}{7}\times\frac{7}{8}\times\frac{8}{9}\)
\(=\frac{1\times2\times3\times4\times5\times6\times7\times8}{2\times3\times4\times5\times6\times7\times8\times9}\)
\(=\frac{1}{9}\)
9/5 + 4/7 + 6/5 + 3/7
= ( 9/5 + 6/5 ) + ( 4/7 + 3/7)
= 3 + 1
= 4
9/5 + 4/7 + 6/5 + 3/7 = (9/5 + 6/5) + (4/7 + 3/7)
= 15/5 + 7/7
= 3 + 1
= 4
1/2 x 45/33 x 1/9 x 11/6 = (1/2 x 1/9) x (45/33 x 11/6)
= 1/18 x 45/18
= 5/2
4/9 x (3/5-1/5) +4/9 -7/5 x 4/9
= 4/9 x 2/5 + 4/9 x 1 - 4/9 x 7/5
= 4/9 x (2/5+1-7/5)
=4/9 x 0
=0.
tick mk nha
HT
4/9 x (3/5-1/5) +4/9 -7/5 x 4/9
= 4/9 x 2/5 + 4/9 x 1 - 4/9 x 7/5
= 4/9 x (2/5+1-7/5)
=4/9 x 0
=0.
a; 60 \(\times\) (\(\dfrac{7}{12}\) + \(\dfrac{4}{15}\))
= 60 \(\times\) \(\dfrac{7}{12}\) + 60 \(\times\) \(\dfrac{4}{15}\)
= 35 + 16
= 51
\(a)\frac{3}{5}\times\frac{2}{5}+\frac{3}{4}\times\frac{3}{5}\)
\(=\frac{3}{5}\times\left(\frac{2}{5}+\frac{3}{4}\right)\)
\(=\frac{3}{5}\times\left(\frac{8}{20}+\frac{15}{20}\right)\)
\(=\frac{3}{5}\times\frac{23}{20}\)
\(=\frac{69}{100}\)
\(b)\frac{5}{9}\times\frac{7}{3}\times\frac{9}{5}\)
\(=\left(\frac{5}{9}\times\frac{9}{5}\right)\times\frac{7}{3}\)
\(=1\times\frac{7}{3}\)
\(=\frac{7}{3}\)
a) 4/9 x 7/5 : 7/9
= (4/9 : 7/9) x 7/5
= (4/9 x 9/7) x 7/5
= 4/7 x 7/5
= 4/5
b) 3/4 x 3/2 + 3/4 x 1/2
= 3/4 x (3/2 + 1/2)
= 3/4 x 4/2
= 3/2
a) \(\dfrac{4}{9}.\dfrac{7}{5}:\dfrac{7}{9}=\dfrac{4}{9}.\dfrac{7}{5}.\dfrac{9}{7}\)
\(=\dfrac{4.7.9}{9.5.7}\)
\(=\dfrac{4}{5}\)
b) \(\dfrac{3}{4}.\dfrac{3}{2}+\dfrac{3}{4}.\dfrac{1}{2}=\dfrac{3}{4}.\left(\dfrac{3}{2}+\dfrac{1}{2}\right)\)
\(=\dfrac{3}{4}.2\)
\(=\dfrac{3}{2}\)