Question

90. Найдите х в пропорциях: 2x + 1 1,3 1) 2) 2,5 0,65 ; = 3,25 13 ; 4x-1,9 0,4 3) 4) an 2,7 9 1 5 2,5 = - 1²/ 5 3x +1 7,2 6x + 1 ; (01 07 5) 6) 1 4 5 3 8 0,75 3x +0,6 2,88 = 0,6 x - 2,8
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Answer 1

$1) \: \: \: \: \: \frac{2x + 1}{1.3} = \frac{2.5}{0.65} \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \\ 0.65(2x + 1) = 2.5 \times 1.3 \: \: \: \: \: \: \\ 1.3x + 0.65 = 3.25 \\ 1.3x = 3.25 - 0.65 \\ 1.3x = 2.6 \\ x = 2$

$2) \: \: \: \: \: \frac{3.25}{4x - 1.9} = \frac{13}{0.4} \: \: \: \: \: \: \: \: \: \: \\ 13(4x - 1.9) = 0.4 \times 3.25 \\ 52x - 24.7 = 1.3 \\ 52x = 24.7 + 1.3 \\ 52x = 26 \\ x = 0.5$

$3) \: \: \: \: \: \frac{2.7}{9} = \frac{1\frac{1}{5} }{3x + 1} \: \: \: \: \: \: \\ 2.7(3x + 1) = 9 \times 1 \frac{1}{5} \\ 8.1x + 2.7 = 9 \times 1.2 \\ 8.1x + 2.7 = 10.8 \\ 8.1x = 10.8 - 2.7 \\ 8.1x = 8.1 \\ x = 1$

$4) \: \: \: \: \: \frac{1 \frac{4}{5} }{2.5} = \frac{7.2}{6x + 1} \: \: \: \: \: \: \: \: \: \\ 1.8(6x + 1) = 2.5 \times 7.2 \\ 10.8x + 1.8 = 18 \\ 10.8x = 18 - 1.8\\ 10.8x= 16.2 \\ x = 1.5$

$5) \: \: \: \: \: \frac{6}{1 \frac{4}{5} } = \frac{3x + 0.6}{2.88} \: \: \: \: \: \: \: \: \: \\ 1.8(3x + 0.6) = 2.88 \times 6 \\ 5.4x + 1.08 = 17.28 \\ 5.4x = 17.28 - 1.08 \\ 5.4x = 16.2 \\ x = 3$

$6) \: \: \: \: \: \frac{ \frac{3}{8} }{0.75} = \frac{0.6}{x - 2.8} \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \\ 0.375(x - 2.8) = 0.75 \times 0.6 \\ 0.375x - 1.05 = 0.45 \\ 0.375x = 0.45 + 1.05 \\ 0.375x = 1.5 \\ x = 4$