\(\dfrac{5}{3}\times\dfrac{15}{8}\times\dfrac{9}{8}\times\dfrac{5}{3}-\dfrac{5}{3}\)
Rút gọn rồi tính:
a) \(\dfrac{3}{9}\times\dfrac{5}{4}\) b) \(\dfrac{10}{15}\times\dfrac{3}{5}\) c) \(\dfrac{5}{8}\times\dfrac{4}{12}\) d) \(\dfrac{9}{27}\times\dfrac{3}{21}\)
a: \(\dfrac{3}{9}\times\dfrac{5}{4}=\dfrac{5}{4}\times\dfrac{1}{3}=\dfrac{5\times1}{4\times3}=\dfrac{5}{12}\)
b: \(\dfrac{10}{15}\times\dfrac{3}{5}=\dfrac{3}{5}\times\dfrac{2}{3}=\dfrac{3\times2}{5\times3}=\dfrac{2}{5}\)
c: \(\dfrac{5}{8}\times\dfrac{4}{12}=\dfrac{5}{8}\times\dfrac{1}{3}=\dfrac{5}{3\times8}=\dfrac{5}{24}\)
d: \(\dfrac{9}{27}\times\dfrac{3}{21}=\dfrac{1}{7}\times\dfrac{1}{3}=\dfrac{1\times1}{7\times3}=\dfrac{1}{21}\)
Rút gọn rồi tính.
a) \(\dfrac{2}{4}\times\dfrac{9}{5}\) b) \(\dfrac{13}{8}\times\dfrac{5}{15}\) c) \(\dfrac{3}{9}\times\dfrac{6}{12}\)
a) \(\dfrac{2}{4}\times\dfrac{9}{5}=\dfrac{1}{2}\times\dfrac{9}{5}=\dfrac{1\times9}{2\times5}=\dfrac{9}{10}\)
b) \(\dfrac{13}{8}\times\dfrac{5}{15}=\dfrac{13}{8}\times\dfrac{1}{3}=\dfrac{13}{24}\)
c) \(\dfrac{3}{9}\times\dfrac{6}{12}=\dfrac{1}{3}\times\dfrac{1}{2}=\dfrac{1}{3\times2}=\dfrac{1}{6}\)
a: =18/20=9/10
b: \(=\dfrac{13\cdot5}{8\cdot15}=\dfrac{13}{8}\cdot\dfrac{1}{3}=\dfrac{13}{24}\)
c: \(=\dfrac{1}{3}\cdot\dfrac{1}{2}=\dfrac{1}{6}\)
Tính:
a) \(\dfrac{2}{5}\times\dfrac{3}{8}\times\dfrac{3}{4}\) b) \(\dfrac{1}{3}\times\dfrac{1}{6}\times\dfrac{1}{9}\)
c) \(\dfrac{3}{4}:\dfrac{1}{5}:\dfrac{7}{8}\) d) \(\dfrac{3}{5}:\dfrac{1}{5}:\dfrac{1}{8}\)
a) $\frac{2}{5} \times \frac{3}{8} \times \frac{3}{4} = \frac{{2 \times 3 \times 3}}{{5 \times 8 \times 4}} = \frac{{18}}{{160}} = \frac{9}{{80}}$
b) $\frac{1}{3} \times \frac{1}{6} \times \frac{1}{9} = \frac{{1 \times 1 \times 1}}{{3 \times 6 \times 9}} = \frac{1}{{162}}$
c) $\frac{3}{4}:\frac{1}{5}:\frac{7}{8} = \frac{3}{4} \times \frac{5}{1} \times \frac{8}{7} = \frac{{3 \times 5 \times 8}}{{4 \times 1 \times 7}} = \frac{{120}}{{28}} = \frac{{30}}{7}$
d) $\frac{3}{5}:\frac{1}{5}:\frac{3}{8} = \frac{3}{5} \times \frac{5}{1} \times \frac{8}{3} = \frac{{3 \times 5 \times 8}}{{5 \times 1 \times 3}} = 8$
\(\dfrac{15}{16}\div\dfrac{5}{8}\times\dfrac{3}{4}\)
\(\dfrac{21}{4}\times\dfrac{16}{14}\times\dfrac{1}{2}\times\dfrac{8}{3}\)
\(\dfrac{15}{16}:\dfrac{5}{8}\times\dfrac{3}{4}\)
\(=\dfrac{15}{16}\times\dfrac{8}{5}\times\dfrac{3}{4}\)
\(=\dfrac{3}{2}\times\dfrac{3}{4}\)
\(=\dfrac{9}{8}\)
_________________
\(\dfrac{21}{4}\times\dfrac{16}{14}\times\dfrac{1}{2}\times\dfrac{8}{3}\)
\(=6\times\dfrac{4}{3}\)
\(=8\)
a) \(\dfrac{-2}{15}\times x=\dfrac{-2}{7}\) b) \(\dfrac{7}{-5}\times x=-3\) c) \(-\dfrac{4}{9}x=\dfrac{1}{2}\) d) \(\dfrac{8}{3}\div x=\dfrac{-3}{8}\)
e) \(x\div\dfrac{3}{-4}=-12\) f) \(\left(-1\right)\div x=\dfrac{-3}{7}+\dfrac{4}{5}\) g)\(\dfrac{4}{11}x-\dfrac{1}{3}=\dfrac{2}{5}\) i) \(\dfrac{-6}{7}-\dfrac{1}{5}x=-4\)
j) \(\dfrac{1}{2}+\dfrac{2}{3}\div7=\dfrac{-1}{3}\) k) \(\dfrac{-5}{2}+x\div7=\dfrac{-1}{3}\) L) \(\dfrac{-3}{2}-\dfrac{1}{4}\div x=-1\)
a: =>x*2/15=2/7
=>x=2/7:2/15=2/7*15/2=15/7
b: x=3:7/5=15/7
c: x=-1/2:4/9=-1/2*9/4=-9/8
d: x=-8/3:3/8=-64/9
g: =>4/11x=2/5+1/3=6/15+5/15=11/15
=>x=11/15:4/11=121/60
l: =>1/4:x=1-3/2=-1/2
=>x=-1/4:1/2=-1/4*2=-1/2
k: =>x:7=-1/3+5/2=-2/6+15/6=13/6
=>x=91/6
a. 4+\(\dfrac{5}{9}\) b. \(\dfrac{8}{3}\)\(-2\) c. \(\dfrac{5}{12}\times\dfrac{4}{15}\) d.\(5:\dfrac{15}{8}\)
a,\(4+\dfrac{5}{9}=\dfrac{4}{1}+\dfrac{5}{9}=\dfrac{36}{9}+\dfrac{5}{9}=\dfrac{41}{9}\)
b,\(\dfrac{8}{3}-2=\dfrac{8}{3}-\dfrac{2}{1}=\dfrac{8}{3}-\dfrac{6}{3}=\dfrac{2}{3}\)
c,\(\dfrac{5}{12}x\dfrac{4}{15}=\dfrac{20}{180}=\dfrac{2}{18}=\dfrac{1}{6}\)
d,\(5:\dfrac{15}{8}=\dfrac{5x8}{15}=\dfrac{40}{15}=\dfrac{8}{3}\)
a.\(4+\dfrac{5}{9}\) b.\(\dfrac{8}{3}-2\) c.\(\dfrac{5}{12}\times\dfrac{4}{15}\) d.\(5:\dfrac{15}{8}\)
a)\(\dfrac{4}{1}+\dfrac{5}{9}=\dfrac{36}{9}+\dfrac{5}{9}=\dfrac{41}{9}\)
b) \(\dfrac{8}{3}-\dfrac{2}{1}=\dfrac{8}{3}-\dfrac{6}{3}=\dfrac{2}{3}\)
\(\dfrac{5}{12}x\dfrac{4}{15}=\dfrac{20}{180}=\dfrac{1}{9}\)
\(\dfrac{5x8}{15}=\dfrac{40}{15}=\dfrac{8}{3}\)
Tính bằng cách thuận tiện.
a) \(\dfrac{3}{5}\times\dfrac{7}{11}\times\dfrac{5}{3}\times11\)
b) \(\dfrac{3}{8}\times\dfrac{2}{7}+\dfrac{5}{7}\times\dfrac{3}{8}\)
a)
\(\dfrac{3}{5}\times\dfrac{7}{11}\times\dfrac{5}{3}\times11\\ =\left(\dfrac{3}{5}\times\dfrac{5}{3}\right)\times\left(\dfrac{7}{11}\times11\right)\\ =\dfrac{3\times5}{5\times3}\times\dfrac{7\times11}{11}\\ =1\times7\\ =7\)
b)
\(\dfrac{3}{8}\times\dfrac{2}{7}+\dfrac{5}{7}\times\dfrac{3}{8}\\ =\dfrac{3}{8}\times\left(\dfrac{2}{7}+\dfrac{5}{7}\right)\\ =\dfrac{3}{8}\times\dfrac{7}{7}\\ =\dfrac{3}{8}\times1=\dfrac{3}{8}\)
C=\(\dfrac{7}{19}\times\dfrac{5}{8}\times\dfrac{-19}{7}\)
D=\(\dfrac{3}{7}\times\dfrac{9}{11}+\dfrac{3}{7}\times\dfrac{2}{11}\)
C)
`7/19xx5/8xx (-19)/7`
`=7/19xx (-19/7)xx5/8`
`= -1xx5/8`
`=-5/8`
D)
`3/7xx9/11+3/7xx2/11`
`=3/7xx(9/11+2/11)`
`=3/7xx11/11`
`=3/7xx1`
`=3/7`