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Bài 1: Tìm y.
\(a)\dfrac{19}{20}-y=\dfrac{8}{5}-\dfrac{3}{4}\\ \dfrac{19}{20}-y=\dfrac{17}{20}\\ y=\dfrac{19}{20}-\dfrac{17}{20}\\ y=\dfrac{2}{20}\\ y=\dfrac{1}{10}\\ b)y:\dfrac{2}{3}=\dfrac{4}{9}\times3\\ y:\dfrac{2}{3}=\dfrac{4}{3}\\ y=\dfrac{4}{3}\times\dfrac{2}{3}\\ y=\dfrac{8}{9}\)
Bài 2: Giải:
Chiều cao của mảnh vườn đó là:
\(\dfrac{2}{3}-\dfrac{1}{4}=\dfrac{5}{12}\left(km\right)\)
Diện tích mảnh vườn đó là:
\(\dfrac{2}{3}\times\dfrac{5}{12}=\dfrac{5}{18}\left(km^2\right)\)
Đáp số: \(\dfrac{5}{18}km^2.\)
Bài 1:
a) \(\dfrac{19}{20}-y=\dfrac{8}{5}-\dfrac{3}{4}\)
\(\dfrac{19}{20}-y=\dfrac{17}{20}\)
\(y=\dfrac{19}{20}-\dfrac{17}{20}\)
\(y=\dfrac{2}{20}=\dfrac{1}{10}\)
b) \(y:\dfrac{2}{3}=\dfrac{4}{9}\times3\)
\(y:\dfrac{2}{3}=\dfrac{4}{3}\)
\(y=\dfrac{4}{3}\times\dfrac{2}{3}\)
\(y=\dfrac{8}{9}\)
Bài 2:
Giải:
Chiều cao của hình bình hành: \(\dfrac{2}{3}\times\dfrac{1}{4}=\dfrac{1}{6}\left(km\right)\)
Diện tích mảnh vườn: \(\dfrac{1}{6}\times\dfrac{2}{3}=\dfrac{1}{9}\left(km^2\right)\)
Đáp số: \(\dfrac{1}{9}km^2\)
`a,`
`Y = 3/5: 5/7`
`Y = 21/25`
`b,`
`y = 1/8: 3/20`
`y = 5/6`
a) \(\dfrac{x}{y}\times\dfrac{3}{4}=\dfrac{5}{6}+\dfrac{1}{3}\)
\(\dfrac{x}{y}\times\dfrac{3}{4}=\dfrac{7}{6}\)
\(\dfrac{x}{y}=\dfrac{7}{6}:\dfrac{3}{4}\)
\(\dfrac{x}{y}=\dfrac{14}{9}\)
b) \(\dfrac{7}{9}:\dfrac{x}{y}=\dfrac{10}{7}-\dfrac{13}{14}\)
\(\dfrac{7}{9}:\dfrac{x}{y}=\dfrac{1}{2}\)
\(\dfrac{x}{y}=\dfrac{7}{9}:\dfrac{1}{2}\)
\(\dfrac{x}{y}=\dfrac{14}{9}\)
a) \(\dfrac{3}{7}+4=\dfrac{3}{7}+\dfrac{4}{1}=\dfrac{3}{7}+\dfrac{28}{7}=\dfrac{31}{7}\)
b) \(\dfrac{5}{9}\times3=\dfrac{5\times3}{9}=\dfrac{15}{9}=\dfrac{5}{3}\)
c) \(\dfrac{7}{8}-\dfrac{2}{9}=\dfrac{63}{72}-\dfrac{16}{72}=\dfrac{47}{72}\)
d) \(5-\dfrac{3}{4}=\dfrac{5}{1}-\dfrac{3}{4}=\dfrac{20}{4}-\dfrac{3}{4}=\dfrac{17}{4}\)
e) \(\dfrac{5}{7}:6=\dfrac{5}{7}:\dfrac{6}{1}=\dfrac{5}{7}\times\dfrac{1}{6}=\dfrac{5}{42}\)
f) \(\dfrac{5}{6}\times\dfrac{2}{7}=\dfrac{5\times2}{6\times7}=\dfrac{10}{42}=\dfrac{5}{21}\)
g) \(3+\dfrac{3}{4}=\dfrac{3}{1}+\dfrac{3}{4}=\dfrac{12}{4}+\dfrac{3}{4}=\dfrac{15}{4}\)
h) \(\dfrac{3}{5}\times\dfrac{4}{8}=\dfrac{3\times4}{5\times8}=\dfrac{12}{40}=\dfrac{3}{10}\)
i) \(5:\dfrac{3}{8}=\dfrac{5}{1}:\dfrac{3}{8}=\dfrac{5}{1}\times\dfrac{8}{3}=\dfrac{40}{3}\)
\(\dfrac{3}{7}+\dfrac{4}{1}=\dfrac{3}{7}+\dfrac{28}{7}=\dfrac{31}{7}\)
\(\dfrac{5}{9}\times3=\dfrac{5}{9}\times\dfrac{3}{1}=\dfrac{15}{9}=\dfrac{5}{3}\)
\(\dfrac{7}{8}-\dfrac{2}{9}=\dfrac{63}{72}-\dfrac{16}{72}=\dfrac{47}{72}\)
\(\dfrac{5}{1}-\dfrac{3}{4}=\dfrac{20}{4}-\dfrac{3}{4}=\dfrac{17}{4}\)
\(\dfrac{5}{7}:\dfrac{6}{1}=\dfrac{5}{7}\times\dfrac{1}{6}=\dfrac{5}{42}\)
\(\dfrac{5}{6}\times\dfrac{2}{7}=\dfrac{5\times2}{6\times7}=\dfrac{10}{42}=\dfrac{5}{21}\)
\(\dfrac{3}{1}+\dfrac{3}{4}=\dfrac{12}{4}+\dfrac{3}{4}=\dfrac{15}{4}\)
\(\dfrac{3}{5}\times\dfrac{4}{8}=\dfrac{3}{5}\times\dfrac{1}{2}=\dfrac{3\times1}{5\times2}=\dfrac{3}{10}\)
\(\dfrac{5}{1}:\dfrac{3}{8}=\dfrac{5}{1}\times\dfrac{8}{3}=\dfrac{40}{3}\)
2/ Tìm y:
y + \(\dfrac{1}{3}\) x 4 = 12 \(\dfrac{2}{5}\) + y = \(\dfrac{12}{35}\) x \(\dfrac{14}{9}\)
\(y=12-\left(\dfrac{1}{3}\times4\right)=12-\dfrac{4}{3}=\dfrac{32}{3}\)
\(y=\left(\dfrac{12}{35}\times\dfrac{14}{9}\right)-\dfrac{2}{5}=\dfrac{8}{15}-\dfrac{2}{5}=\dfrac{2}{15}\)
1)
a)\(\dfrac{20}{30}+\dfrac{9}{30}=\dfrac{29}{30}\)
b)\(\dfrac{16}{24}-\dfrac{15}{24}=\dfrac{1}{24}\)
c)\(\dfrac{12}{63}=\dfrac{4}{21}\)
d) \(\dfrac{5}{6}x\dfrac{3}{4}=\dfrac{15}{24}=\dfrac{5}{8}\)
2)
a)\(x=\dfrac{5}{4}-\dfrac{2}{3}\)
\(x=\dfrac{7}{12}\)
b) \(x=4x\dfrac{3}{5}\)
\(x=\dfrac{12}{5}\)
a) \(\dfrac{2}{5}\times?=\dfrac{3}{10}\)
\(?=\dfrac{3}{10}:\dfrac{2}{5}=\dfrac{3}{4}\)
b) \(\dfrac{1}{8}:?=\dfrac{1}{5}\)
\(?=\dfrac{1}{8}:\dfrac{1}{5}=\dfrac{5}{8}\)
a: Phân số cần tìm là: \(\dfrac{3}{10}:\dfrac{2}{5}=\dfrac{3}{10}\cdot\dfrac{5}{2}=\dfrac{15}{20}=\dfrac{3}{4}\)
b: Phân số cần tìm là \(\dfrac{1}{8}:\dfrac{1}{5}=\dfrac{5}{8}\)
\(a,x-\dfrac{5}{7}=\dfrac{3}{5}\times\dfrac{1}{2}\)
\(x-\dfrac{5}{7}=\dfrac{3}{10}\)
\(x=\dfrac{3}{10}+\dfrac{5}{7}\)
\(x=\dfrac{21}{70}+\dfrac{50}{70}\)
\(x=\dfrac{71}{70}\)
\(Vayx=\dfrac{71}{70}\)
\(b,x\times\dfrac{2}{3}=\dfrac{5}{8}+\dfrac{3}{4}\)
\(x\times\dfrac{2}{3}=\dfrac{5}{8}+\dfrac{6}{8}\)
\(x\times\dfrac{2}{3}=\dfrac{11}{8}\)
\(x=\dfrac{11}{8}:\dfrac{2}{3}\)
\(x=\dfrac{11}{8}\times\dfrac{3}{2}\)
\(x=\dfrac{33}{16}\)
\(Vayx=\dfrac{33}{16}\)
`7/2 : y= 3/8 + 5/4`
`=> 7/2 : y= 3/8 +10/8`
`=> 7/2 : y=13/8`
`=> y= 7/2 : 13/8`
`=> y= 7/2 xx 8/13`
`=> y= 28/13`
\(\dfrac{7}{2}:y=\dfrac{3}{8}+\dfrac{5}{4}\)
\(\dfrac{7}{2}:y=\dfrac{13}{8}\)
\(y=\dfrac{7}{2}:\dfrac{13}{8}\)
\(y=\dfrac{7}{2}\times\dfrac{8}{13}\)
\(y=\dfrac{28}{13}\)