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ta có: \(\hept{\begin{cases}8\frac{3}{4}=\frac{8\times4+3}{4}=\frac{35}{4}\\4\frac{1}{5}=\frac{4\times5+1}{5}=\frac{21}{5}\\3\frac{3}{4}=\frac{3\times4+3}{4}=\frac{15}{4}\end{cases}}\)
A)6 và 4/5-(1 và 2/3+3 và 4/5)
=6+4/5-1-2/3-3-4/5
=(6-1-3)+(4/5-4/5)-2/3
=2-2/3=1 và 1/3
B)[(19+5/8/7/12)-(13+1/4/7/12)]X4/5
=[(19-13)+(5/8/7/12-1/4/7/12)]X4/5
=[6+3/8/7/12]X4/5
=[6+9/14]X4/5
=93/14 X4/5=186/35
nhớ
X đầu tiên : 32 phần 32
X thứ hai : 36 phần 120
X thứ ba : 18 phần 21
X - ( 1/4 + 1/8 ) = 5/8
X - 3/8 = 5/8
X = 5/8 + 3/8
X = 1
\(a.32,5-3\cdot0,87=32,5-2,61=29,89\)
\(8,5\cdot\left(1\dfrac{1}{2}+\dfrac{4}{4}\right):5=8,5\cdot\left(\dfrac{3}{2}+\dfrac{4}{4}\right):5\\ =8,5\cdot\left(\dfrac{6}{4}+\dfrac{4}{4}\right):5\\ =8,5\cdot\dfrac{10}{4}:5\\ =\dfrac{85}{4}:5\\ =\dfrac{17}{4}\)
\(b.30,96-6,45+14,4:3=30,96-6,45+4,8\\ =29,31\)
\(\dfrac{2}{5}\cdot\left(\dfrac{4}{5}-\dfrac{1}{2}\right)=\dfrac{2}{5}\cdot\left(\dfrac{8}{10}-\dfrac{5}{10}\right)\\ =\dfrac{2}{5}\cdot\dfrac{3}{10}=\dfrac{3}{25}\)
bài 2
\(a.2,5\cdot12,5\cdot8\cdot0,4=\left(2,5\cdot0,4\right)\left(12,5\cdot8\right)\\ =1\cdot100=100\)
b,\(\dfrac{12}{15}\cdot\dfrac{5}{6}\cdot\dfrac{3}{20}\cdot\dfrac{32}{5}=\dfrac{12\cdot5\cdot3\cdot32}{15\cdot6\cdot20\cdot5}\\ =\dfrac{3\cdot4\cdot5\cdot3\cdot4\cdot8}{3\cdot5\cdot2\cdot3\cdot5\cdot4\cdot5}=\dfrac{16}{25}\)
Bài 1:
a) \(32.5-3\cdot0.87=32.5-2.61=29.89\)
\(8.5\cdot\left(1\dfrac{1}{2}+\dfrac{4}{4}\right):5=8.5\cdot\dfrac{5}{2}:5=\dfrac{17}{2}\cdot\dfrac{5}{2}:5=\dfrac{85}{4}\cdot\dfrac{1}{5}=\dfrac{17}{4}\)
` a) 4 8/23 + 5 7/8 - 9 8/23 `
`= 100/23 + 47/8 - 215/23 `
`= ( 100/23 - 215/23) + 47/8 `
`= -115/23 + 47/8 `
`= -5 + 47/8 `
`= -5/1 + 47/8 `
`= -40/8 + 47/8 `
`=7/8`
`b) 8 2/7 - ( 3 4/9 + 4 2/7 ) `
`= 58/7 - 31/9 - 30/7 `
`= (58/7 - 30/7 ) - 31/9 `
`= 28/7 - 31/9 `
` = 252/63 - 217/63 `
`= 35/63`
`= 5/9`
`@ animephamdanhv.`
a)\(4\dfrac{8}{23}+5\dfrac{7}{8}-9\dfrac{8}{23}=\dfrac{100}{23}+\dfrac{47}{8}-\dfrac{215}{23}=\dfrac{100}{23}-\dfrac{215}{23}+\dfrac{47}{8}=-\dfrac{115}{23}+\dfrac{47}{8}=-5+\dfrac{47}{8}=\dfrac{7}{8}\)
b) \(8\dfrac{2}{7}-\left(3\dfrac{4}{9}+4\dfrac{2}{7}\right)=\dfrac{58}{7}-\left(\dfrac{31}{9}+\dfrac{30}{7}\right)=\dfrac{58}{7}-\dfrac{31}{9}-\dfrac{30}{7}=\dfrac{58}{7}-\dfrac{30}{7}-\dfrac{31}{9}=4-\dfrac{31}{9}=\dfrac{5}{9}\)
a) \(\left(8\frac{4}{5}x-50\right):0,4=5\)
\(\Rightarrow\left(\frac{44}{5}x-50\right)=5.0,4\)
\(\Rightarrow\frac{44}{5}x-50=2\)
\(\Rightarrow\frac{44}{5}x=2+50\)
\(\Rightarrow\frac{44}{5}x=52\)
\(\Rightarrow x=\frac{65}{11}\)
b) \(\left(\frac{5x}{3}-3\right):15=\frac{3}{10}\)
\(\Rightarrow\frac{5x}{3}-3=\frac{3}{10}.15\)
\(\Rightarrow\frac{5x}{3}-3=\frac{45}{10}\)
\(\Rightarrow\frac{5x}{3}=\frac{45}{10}+3\)
\(\Rightarrow\frac{5x}{3}=\frac{15}{2}\)
\(\Rightarrow5x.2=3.15\)
=> 5x.2 = 45
=> 5x = 45 : 2
=> 5x = 45/2
=> x = 9/2
Đề đây phải ko bn?
\(8\frac{3}{4}+4\frac{1}{5}-3\frac{3}{4}\)
ko hiểu tai sao lại 8 và 3 phần 4 thế là thế nào