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\(=15x\left(\dfrac{21}{43}+\dfrac{22}{43}\right)=15x1=15\)
\(\frac{\left(2005+1\right).125+1000}{\left(125+1\right).2005-888}\)
= \(\frac{2005.125+125+1000}{125.2005+2005-888}\)
= \(\frac{2005.125+1125}{125.2005+1117}\)
= \(\frac{250625+1125}{250625+1117}\)
= \(\frac{125875}{125871}\)
\(1,\\ a,=\dfrac{7}{19}\times\left(\dfrac{1}{3}+\dfrac{2}{3}\right)=\dfrac{7}{19}\times1=\dfrac{7}{19}\\ b,=\dfrac{2}{5}+\left(\dfrac{3}{4}+\dfrac{1}{4}\right)=\dfrac{2}{5}+1=\dfrac{7}{5}\\ 2,\\ a,=15\times\left(\dfrac{2121}{4343}+\dfrac{222222}{434343}\right)\\ =15\times\left(\dfrac{2121:101}{4343:101}+\dfrac{222222:10101}{434343:10101}\right)\\ =15\times\left(\dfrac{21}{43}+\dfrac{22}{43}\right)=15\times\dfrac{43}{43}=15\times1=15\)
\(3,\)
Cạnh \(AC=\) chu vi ABC \(-AB-BC=\dfrac{4}{5}-\dfrac{1}{5}-\dfrac{1}{4}=\dfrac{3}{5}-\dfrac{1}{4}=\dfrac{7}{20}\left(m\right)\)
Vì \(\dfrac{7}{20}>\dfrac{5}{20}>\dfrac{4}{20}\Rightarrow\dfrac{7}{20}>\dfrac{1}{4}>\dfrac{1}{5}\) nên \(AC>BC>AB\)
x - 4\(\dfrac{9}{11}\) = \(\dfrac{2121}{2222}\)
\(x+7\dfrac{4}{5}=9\dfrac{7}{15}\)
\(=>x+\dfrac{39}{5}=\dfrac{142}{15}\)
\(=>x=\dfrac{142}{15}-\dfrac{39}{5}=\dfrac{142}{15}-\dfrac{117}{15}\)
\(=>x=\dfrac{25}{15}=\dfrac{5}{3}\)
___________
\(x-4\dfrac{9}{11}=\dfrac{2121}{2222}\)
\(=>x-\dfrac{53}{11}=\dfrac{21}{22}\)
\(=>x=\dfrac{21}{22}+\dfrac{53}{11}=\dfrac{21}{22}+\dfrac{106}{22}\)
\(=>x=\dfrac{127}{22}\)
\(x+7\dfrac{4}{5}=9\dfrac{7}{15}\)
\(x=9\dfrac{7}{15}-7\dfrac{4}{5}\)
\(x=\left(9-7\right)+\left(\dfrac{7}{15}-\dfrac{4}{5}\right)\)
\(x=2\dfrac{-1}{3}=\dfrac{5}{3}\)
\(x=\dfrac{2121:101}{2222:101}+4\dfrac{9}{11}\)
\(x=\dfrac{21}{22}+4\dfrac{18}{22}\)
\(x=\dfrac{21+4\cdot22+18}{22}=\dfrac{127}{22}\)
\(\dfrac{15}{10}=1,5;\dfrac{35}{100}=0,35;\dfrac{107}{100}=1,07\)
\(\dfrac{22109}{1000}=22,109;\dfrac{14}{5}=\dfrac{28}{10}=2,8;\dfrac{920}{1000}=0,92\)
\(\dfrac{138}{100}=1,38;\dfrac{2007}{10}=200,7;\dfrac{1}{1000}=0,001\)
1,5
0,35
1,007
22,109
2,8
0,92
1,38
200,7
0,001
Bài 1
a; \(\dfrac{7}{19}\) x \(\dfrac{1}{3}\) + \(\dfrac{7}{19}\) x \(\dfrac{2}{3}\)
= \(\dfrac{7}{19}\) x (\(\dfrac{1}{3}+\dfrac{2}{3}\))
= \(\dfrac{7}{19}\) x 1
= \(\dfrac{7}{19}\)
b; 15 x \(\dfrac{2121}{4343}\) + 15 x \(\dfrac{212121}{434343}\)
= 15 x \(\dfrac{21}{43}\) + 15 x \(\dfrac{21}{43}\)
= 15 x \(\dfrac{21}{43}\) x (1 + 1)
= 15 x \(\dfrac{21}{43}\) x 2
= (15 x 2) x \(\dfrac{21}{43}\)
= 30 x \(\dfrac{21}{43}\)
= \(\dfrac{630}{43}\)
Bài 7: Tính
a) \(4\dfrac{2}{5}\times8\dfrac{3}{4}-2\dfrac{3}{4}\)
\(=\dfrac{22}{5}\times\dfrac{35}{4}-\dfrac{11}{4}\)
\(=\dfrac{77}{2}-\dfrac{11}{4}\)
\(=\dfrac{143}{4}\)
b) \(2\dfrac{2}{3}+1\dfrac{2}{5}-\dfrac{2}{15}\)
\(=\dfrac{8}{3}+\dfrac{7}{5}-\dfrac{2}{15}\)
\(=\dfrac{47}{15}-\dfrac{2}{15}\)
\(=\dfrac{45}{15}=3\)
c) \(3\dfrac{1}{3}-2\dfrac{2}{3}+1\dfrac{5}{6}\)
\(=\dfrac{10}{3}-\dfrac{8}{3}+\dfrac{11}{6}\)
\(=\dfrac{2}{3}+\dfrac{11}{6}\)
\(=\dfrac{15}{6}\)
\(a,=15\left(\dfrac{2121}{4343}+\dfrac{222222}{434343}\right)=15\left(\dfrac{21}{43}+\dfrac{22}{43}\right)=15\cdot1=15\)