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\(a,\dfrac{6}{11}+6+\dfrac{5}{7}=\dfrac{42+462+55}{77}=\dfrac{559}{77}\)
\(b,\dfrac{9}{8}\times\dfrac{3}{12}:\dfrac{5}{9}=\dfrac{9}{8}\times\dfrac{3}{12}\times\dfrac{9}{5}=\dfrac{243}{480}=\dfrac{81}{160}\)
\(c,\dfrac{8}{7}:4+2=\dfrac{8}{7}\times\dfrac{1}{4}+2=\dfrac{8}{28}+2=\dfrac{2}{7}+2=\dfrac{16}{7}\)
\(d,\dfrac{3}{5}+4:\dfrac{6}{4}=\dfrac{3}{5}+4\times\dfrac{4}{6}=\dfrac{3}{5}+\dfrac{8}{3}=\dfrac{49}{15}\)
A)\(\dfrac{7}{20}-\left(\dfrac{5}{8}-\dfrac{2}{5}\right)\)
\(=\dfrac{7}{20}-\left(\dfrac{25}{40}-\dfrac{16}{40}\right)\)
\(=\dfrac{7}{20}-\dfrac{9}{40}\)
\(=\dfrac{14}{40}-\dfrac{9}{40}=\dfrac{5}{40}=\dfrac{1}{8}\)
B) \(\dfrac{5}{6}+\left(\dfrac{5}{9}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{6}+\left(\dfrac{20}{36}-\dfrac{9}{36}\right)\)
\(=\dfrac{5}{6}+\dfrac{11}{36}\).
\(=\dfrac{30}{36}+\dfrac{11}{36}=\dfrac{41}{36}\)
C) \(\dfrac{9}{10}-\left(\dfrac{2}{5}-\dfrac{3}{10}\right)+\dfrac{7}{20}\)
\(=\dfrac{9}{10}-\left(\dfrac{4}{10}-\dfrac{3}{10}\right)+\dfrac{7}{20}\)
\(=\dfrac{9}{10}-\dfrac{1}{10}+\dfrac{7}{20}\)
\(=\dfrac{18}{20}-\dfrac{2}{20}+\dfrac{7}{20}=\dfrac{23}{20}\)
a: =7/20-5/8+2/5
=14/40-25/40+16/40
=5/40=1/8
b: =5/6+5/9-1/4
=30/36+20/36-9/36
=41/36
c: =9/10-2/5+3/10+7/20
=12/10-2/5+7/20
=7/20+6/5-2/5
=7/20+4/5
=7/20+16/20
=23/20
Bài 1:
a: x+1/2=5/6
nên x=5/6-1/2=1/3
b: x+1/4=3/4
nên x=3/4-1/4=2/4=1/2
c: x+3/10=1/2
nên x=1/2-3/10=5/10-3/10=1/5
d: x+1/4=3/8
nên x=3/8-1/4=3/8-2/8=1/8
a) Nếu a = 6, b = 9 và c = 20 thì a + b + c = 6 + 9 + 20 = 35
b) Nếu a = 17, b = 5 và c = 8 thì a + b + c = 17 + 5 + 8 = 30
a)
Thay `a = 6; b = 9; c = 20`
`6 + 9 + 20 = 15 + 20 = 35`
Vậy, với `a = 6; b = 9; c = 20` thì `a + b + c = 35`
b)
Thay `a = 17; b = 5; c = 8`
`17 + 5 + 8 = 22 + 8 = 30`
Vậy, với `a = 17; b = 5; c = 8` thì `a + b + c = 30.`
Câu a đáp án D Câu b đáp án A
\(a,\left(\frac{9}{8}+\frac{5}{6}\right)\times\frac{6}{5}=\left(\frac{9\times3}{8\times3}+\frac{5\times4}{6\times4}\right)\times\frac{6}{5}=\left(\frac{27}{24}+\frac{20}{24}\right)\times\frac{6}{5}=\frac{47}{24}\times\frac{6}{5}=\frac{47\times6}{24\times5}\)\(=\frac{47\times1}{4\times5}=\frac{47}{20}\)
\(b,\left(\frac{7}{12}+\frac{3}{4}\right)\div\frac{4}{5}=\left(\frac{7}{12}+\frac{3\times3}{4\times3}\right)\div\frac{4}{5}=\left(\frac{7}{12}+\frac{9}{12}\right)\div\frac{4}{5}=\frac{16}{12}\times\frac{4}{5}\)\(=\frac{16\div4}{12\div4}\div\frac{4}{5}=\frac{4}{3}\div\frac{4}{5}=\frac{4}{3}\times\frac{5}{4}=\frac{4\times5}{3\times4}=\frac{5}{3}\)
đó
ht