515/2323 1x 696969 / 545454 x 2727/1515
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\(=\dfrac{15}{23}\times\dfrac{69}{54}\times\dfrac{27}{15}\\ =\dfrac{3}{2}\)
a. \(\left(\dfrac{17}{2}+\dfrac{1}{2}+1\right).\dfrac{4}{7}\)
\(=\dfrac{19}{2}.\dfrac{4}{7}=\dfrac{38}{7}\)
b. \(\dfrac{2727}{2323}.\dfrac{69}{54}\)
\(=\dfrac{27}{23}.\dfrac{23.3}{27.2}=\dfrac{3}{2}\)
2. Chiều cao hình bình hành là: 1200 : 60 = 20 cm
a, \(\dfrac{17}{2}\) \(\times\) \(\dfrac{4}{7}\) + \(\dfrac{4}{7}\) \(\times\) \(\dfrac{1}{2}\) + \(\dfrac{4}{7}\) b, \(\dfrac{1515}{2323}\) \(\times\) \(\dfrac{69}{54}\) \(\times\) \(\dfrac{2727}{1515}\)
= \(\dfrac{17}{2}\) \(\times\) \(\dfrac{4}{7}\) + \(\dfrac{4}{7}\) \(\times\) \(\dfrac{1}{2}\) + \(\dfrac{4}{7}\) \(\times\) 1 = \(\dfrac{15}{23}\) \(\times\) \(\dfrac{23}{18}\) \(\times\) \(\dfrac{27}{15}\)
= \(\dfrac{4}{7}\) \(\times\) ( \(\dfrac{17}{2}\) + \(\dfrac{1}{2}\) + 1) = \(\dfrac{27}{18}\)
= \(\dfrac{4}{7}\) \(\times\) ( 9 + 1) = \(\dfrac{3}{2}\)
= \(\dfrac{4}{7}\times10\)
= \(\dfrac{40}{7}\)
Bài 2: Chiều cao của hình bình hành là:
1200 : 60 = 20 cm
Đổi 20 cm = 2 dm
Đáp số: 2 dm
\(\frac{1010+1111+1212+1313+1414+1515+1616+1717}{2020+2121+2222+2323+2424+2525+2626+2727}\)
\(=\frac{101.10+101.11+...+101.17}{101.20+101.21+...+101.27}\)
\(=\frac{101.\left(10+11+...+17\right)}{101.\left(20+21+...+27\right)}\)
\(=\frac{108}{188}\)
\(=\frac{27}{47}\)
\(2>\left(\frac{1}{6}+\frac{2}{15}+\frac{3}{40}+\frac{4}{96}\right)\cdot5.y>\frac{5}{6}\)
\(\Rightarrow2>\left(\frac{1}{6}+\frac{2}{15}+\frac{3}{40}+\frac{1}{24}\right):5.y>\frac{5}{6}\)
\(\Rightarrow2>\left(\frac{20}{120}+\frac{16}{120}+\frac{9}{120}+\frac{5}{120}\right):5.y>\frac{5}{6}\)
\(\Rightarrow2>\frac{5}{12}:5.y>\frac{5}{6}\)
\(\Rightarrow2>\frac{1}{12}.y>\frac{5}{6}\)
Đặt :\(\frac{1}{12}.y=2\Rightarrow y=2:\frac{1}{12}=24\)
\(\frac{1}{12}.y=\frac{5}{6}\Rightarrow y=\frac{5}{6}:\frac{1}{12}=10\)
\(\Rightarrow24>y>10\)
\(\Rightarrow y\in\left\{11;12;...;23\right\}\)
\(\frac{1212}{1515}:\frac{2727}{2525}\)
\(=\frac{1212}{1515}x\frac{2525}{2727}\)
\(=\frac{20}{27}\)
Chúc Học tốt
\(\frac{1212}{1515}:\frac{2727}{2525}=\frac{1212}{1515}x\frac{2525}{2727}=\frac{12x101}{15x101}x\frac{25x101}{27x101}=\frac{12x25}{15x27}=\frac{3x4x5x5}{3x5x27}=\frac{4x5}{27}=\frac{20}{27}.\)