Tìm x,biết
6/8=15/x
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Bài giải:
Đổi: 7km 50m = 7 050m
Vì vậy 7km 50m < 7500m
Đáp án B
Câu 1:
\(\left(1\right)x\cdot1,5:2,4=0,3\\ x\cdot0,625=0,3\\ x=0,3:0,625\\ x=0,48\\ \left(2\right)\dfrac{3}{7}+\dfrac{1}{7}:x=1\\ \dfrac{1}{7}:x=1-\dfrac{3}{7}\\ \dfrac{1}{7}:x=\dfrac{4}{7}\\ x=\dfrac{1}{7}:\dfrac{4}{7}\\ x=\dfrac{1}{4}\\ O\left(3\right)\left(\dfrac{3}{4}\cdot31\dfrac{11}{23}+0,75\cdot\dfrac{12}{23}\right)\left(x-1\right)=24\\ \left(\dfrac{3}{4}\cdot31\dfrac{11}{23}+\dfrac{3}{4}\cdot\dfrac{12}{23}\right)\left(x-1\right)=24\\ \dfrac{3}{4}\cdot\left(31+\dfrac{11}{23}+\dfrac{11}{23}\right)\left(x-1\right)=24\\ \dfrac{3}{4}\cdot32\left(x-1\right)=24\\ 24\left(x-1\right)=24\\ x-1=1\\ x=2\\ \left(4\right)x-\dfrac{\dfrac{1}{3}-0,25+\dfrac{1}{5}}{1\dfrac{1}{6}-0,875+0,7}=2022\\ x-\dfrac{\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{5}}{\dfrac{7}{6}-\dfrac{7}{8}+\dfrac{7}{10}}=2022\\ x-\dfrac{\dfrac{2}{3}-\dfrac{2}{8}+\dfrac{2}{10}}{\dfrac{7}{6}-\dfrac{7}{8}+\dfrac{7}{10}}=2022\\ x-\dfrac{2\left(\dfrac{1}{3}-\dfrac{1}{8}+\dfrac{1}{10}\right)}{7\left(\dfrac{1}{6}-\dfrac{1}{8}+\dfrac{1}{10}\right)}=2022\\ x-\dfrac{2}{7}=2022\\ x=2022+\dfrac{2}{7}=\dfrac{14156}{7}\)
\(\dfrac{BC}{5}=\dfrac{150}{35}\Rightarrow BC=\dfrac{150}{7}m\)
a) 5.(x-7)=0
x-7=0:5
x-7=0
x=0+7
x=7
b) 17.(15.x-45)=0
15x-45=0:17
15x-45=0
15x=0+45
15x=45
x=45:15
x=3
c) 15+4(x-2)=95
15+4x-8=95
4x+7=95
4x=95-7
4x=88
x=88:4
x=22
d) 140-[25:(x-11)+4]=131
25:(x-11)+4=140-131
25:(x-11)+4=9
25:(x-11)=9-4
25:(x-11)=5
x-11=25:5
x-11=5
x=5+11
x=16
câu c;
15 + 4 \(\times\) (\(x\) - 2) = 95
4 \(\times\) (\(x\) - 2) = 95 - 15
4 \(\times\) (\(x\) - 2) = 80
\(x\) - 2 = 80 : 4
\(x\) - 2 = 20
\(x\) = 20 + 2
\(x=22\)
\(\dfrac{6}{8}=\dfrac{15}{x}\\ \Rightarrow6\times x=15\times8\\ \Rightarrow6\times x=120\\ \Rightarrow x=120:6\\ \Rightarrow x=20\)
Vậy \(x=20\)