Question

1. Calcule o valor de X nas proporções abaixo:


a) X X + 3
------- = ---------
6 15


b) 3 5X
------ = ------
4 20


c) 6 9
-------- = ---------
X 12


d) 8 4
-------- = ---------
5 X

e) X 2
------- = --------
15 3

Answer 1

Explicação passo-a-passo:

a)

$\sf \dfrac{x}{6}=\dfrac{x+3}{15}$

$\sf 15x=6\cdot(x+3)$

$\sf 15x=6x+18$

$\sf 15x-6x=18$

$\sf 9x=18$

$\sf x=\dfrac{18}{9}$

$\sf \red{x=2}$

b)

$\sf \dfrac{3}{4}=\dfrac{5x}{20}$

$\sf 4\cdot5x=3\cdot20$

$\sf 20x=60$

$\sf x=\dfrac{60}{20}$

$\sf \red{x=3}$

c)

$\sf \dfrac{6}{x}=\dfrac{9}{12}$

$\sf 9x=6\cdot12$

$\sf 9x=72$

$\sf x=\dfrac{72}{9}$

$\sf \red{x=8}$

d)

$\sf \dfrac{8}{5}=\dfrac{4}{x}$

$\sf 8x=5\cdot4$

$\sf 8x=20$

$\sf x=\dfrac{20}{8}$

$\sf x=\dfrac{5}{2}$

$\sf \red{x=2,5}$

e)

$\sf \dfrac{x}{15}=\dfrac{2}{3}$

$\sf 3x=15\cdot2$

$\sf 3x=30$

$\sf x=\dfrac{30}{3}$

$\sf \red{x=10}$