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\(\dfrac{21}{16}\times\dfrac{8}{5}\times\dfrac{15}{7}=\dfrac{21\times8\times15}{16\times5\times7}=\dfrac{7\times3\times8\times5\times3}{8\times2\times5\times7}=\dfrac{3\times3}{2}=\dfrac{9}{2}\)
\(\dfrac{18}{9}\times\dfrac{9}{36}\times\dfrac{27}{3}=2\times\dfrac{1}{4}\times9=\dfrac{1}{2}\times9=\dfrac{9}{2}\)
a)\(=\dfrac{3}{3}+\dfrac{4}{3}=\dfrac{7}{3}\)
b)\(=\dfrac{5}{9}\times\dfrac{3}{2}=\dfrac{15}{18}=\dfrac{5}{6}\)
d)\(=\left(\dfrac{12}{8}-\dfrac{3}{8}\right)\times2=\dfrac{9}{8}\times2=\dfrac{18}{8}=\dfrac{9}{4}\)
c)\(=\dfrac{4}{3}-\dfrac{5}{6}=\dfrac{8}{6}-\dfrac{5}{6}=\dfrac{3}{6}=\dfrac{1}{2}\)
a) 1 + 4/3 = 7/3
b) 5/9 : 2/3 = 5/6
c ) 4/3 -1/3 x 5/2
= 1 x 5/2
= 5/2
d) ( 3/2 - 3/8) : 1/2
= 9/8 : 1/2
= 9/4
e) 15/16 : 3/8 x 3/4
= 5/2 x 3/4
= 15/8
f) 7/19 x 1/3 x 7/19 x 2/3
= 7/19 x (1/3 x 2/3)
= 7/19 x 2/9
= 14/171
g) 3/5 x 8/27 x 25/3
= 3/5 x 25/3 x 8/27
= 5 x 8/27
= 40/27
h) 1/5 + 4/11 + 4/5 + 7/11
= (1/5 + 4/5) + (4/11 + 7/11)
= 1 + 1
= 2
2/5 + 3/4 - 4/7 = 23/20 - 4/7 = 81/140
7/9 : 2/3 x 5/4 = 7/6 x 5/4 = 35/24
4/5 x (7/10 - 1/2) = 4/5 x 1/5 = 4/25
a) \(\dfrac{2}{5}+\dfrac{3}{4}-\dfrac{4}{7}\)
\(=\dfrac{56}{140}+\dfrac{105}{140}-\dfrac{80}{140}\)
\(=\dfrac{56+105-80}{140}\)
\(=\dfrac{81}{140}\)
b) \(\dfrac{7}{9}:\dfrac{2}{3}\times\dfrac{5}{4}\)
\(=\dfrac{7}{9}\times\dfrac{3}{2}\times\dfrac{5}{4}\)
\(=\dfrac{7\times3\times5}{9\times2\times4}\)
\(=\dfrac{35}{24}\)
c) \(\dfrac{4}{5}\times\left(\dfrac{7}{10}-\dfrac{1}{2}\right)\)
\(=\dfrac{4}{5}\times\left(\dfrac{7}{10}-\dfrac{5}{10}\right)\)
\(=\dfrac{4}{5}\times\dfrac{1}{5}\)
\(=\dfrac{4}{25}\)
Sure=)
Simple task:)
Tính bằng cách thuận tiện nhất :
3/7 + 1/8 + 4/7 + 7/8
a. 2
b. 1 + 1
c. 2 + 1
d. ( 3/7 + 1/8 ) + ( 4/7 + 7/8 )
e. 3
g. 1 + 2
h. ( 3/7 + 4/7 ) + ( 1/8 + 7/8 )
7/8 x 1/4 + 7/8 x 2/4 + 7/8
=7/8 x\(\left(\dfrac{1}{4}+\dfrac{2}{4}\right)\) + 7/8
=7/8 x 3/4 + 7/8
=7/8 x \(\left(\dfrac{3}{4}+1\right)\)
=7/8 x 7/4
=49/32
\(\dfrac{7}{8}:5\times\dfrac{1}{7}\\ =\dfrac{7}{8}\times\dfrac{1}{5}\times\dfrac{1}{7}\\ =\dfrac{7\times1\times1}{8\times5\times7}\\ =\dfrac{1}{8\times5}=\dfrac{1}{40}\)