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Phân số bé hơn 1 là \(B.\frac{15}{18}\)và \(D.\frac{20}{21}\)
\(\frac{9}{11}\)< \(\frac{13}{15}\)
\(\frac{19}{15}\)< \(\frac{15}{11}\)
1. Rút gọn
\(\frac{8x20x4}{9x20x4}=\frac{8}{9}\)
\(\frac{7x9x12}{6x14x18}=\frac{1x1x2}{1x2x2}=\frac{2}{4}=\frac{1}{2}\)
\(\frac{2x3x5}{4x9x10}=\frac{1x1x1}{2x3x2}=\frac{1}{12}\)
2. tìm x
\(\frac{x}{27}=\frac{12}{18}\)
\(\frac{x}{27}=\frac{2}{3}\)
=> X x 3 = 27 x 2
X x 3 = 54
X = 54 : 3
X = 18
\(\frac{35}{49}=\frac{10}{x}\)
\(\frac{5}{7}=\frac{10}{x}\)
=> 5 x X = 7 x 10
5 x X = 70
X = 70 : 5
X = 14
1. \(\frac{8.20.4}{9.20.4}\)= \(\frac{8}{9}\)
\(\frac{7.9.12}{6.14.18}\)= \(\frac{7.9.6.2}{6.7.2.9.2}\)= \(\frac{1}{2}\)
\(\frac{2.3.5}{4.9.10}\)= \(\frac{2.3.5}{2.2.3.3.2.5}\)= \(\frac{1}{12}\)
2. \(\frac{x}{27}\)= \(\frac{12}{18}\) \(\frac{35}{49}\)= \(\frac{10}{x}\)
Ta có : \(\frac{12}{18}\)= \(\frac{6}{9}\) Ta có : \(\frac{35}{49}\)= \(\frac{70}{98}\)
Mà \(\frac{x}{27}\)= \(\frac{6}{9}\) Mà \(\frac{10}{x}\)= \(\frac{70}{98}\)
\(\Rightarrow\)\(x\)= \(27:9.6\) \(\Rightarrow\)\(x\)= \(98:\left(70:10\right)\)
Chú ý : '' \(.\)" là dấu nhân.
\(1,\frac{3}{5}+\frac{7}{2}-\frac{4}{7}=\frac{42}{70}+\frac{245}{70}-\frac{40}{70}=\frac{247}{70}\)
\(2,\frac{4}{5}-\frac{1}{3}+\frac{3}{4}=\frac{48}{60}-\frac{20}{60}+\frac{45}{60}=\frac{73}{60}\)
\(3,\frac{1}{3}\times\frac{5}{7}:\frac{7}{2}=\frac{5}{21}:\frac{7}{2}=\frac{10}{147}\)
\(4,\frac{1}{2}:\frac{2}{7}\times\frac{4}{7}=\frac{7}{4}\times\frac{4}{7}=1\)
\(5,\frac{19}{15}\times\frac{3}{7}:\frac{4}{9}=\frac{19}{35}:\frac{4}{9}=\frac{171}{140}\)
\(6,\frac{11}{3}:\frac{9}{16}:\frac{3}{8}=\frac{176}{27}:\frac{3}{8}=\frac{1408}{81}\)
_Chúc bạn học tốt _
ta có: \(\frac{12}{27}=\frac{4}{9}\)
mà\(\frac{25}{45}=\frac{5}{9};\frac{20}{45}=\frac{4}{9};\frac{40}{42}=\frac{20}{21};\frac{32}{72}=\frac{4}{9};\frac{15}{27}=\frac{5}{9}\)
\(\Rightarrow\frac{12}{27}=\frac{20}{45}=\frac{32}{72}\left(=\frac{4}{9}\right)\)
CHÚC BN HỌC TỐT!
Đáp án là C: \(\frac{15}{27}\)
_Trả lời :
\(C.\frac{15}{27}\)
Vì \(\frac{5}{9}=\frac{5\cdot3}{9\cdot3}=\frac{15}{27}\)