Question

3 ) Calcule o valor de x nas proporções:

a )
$\frac{x}{5} = \frac{6}{10}$

b )
$\frac{3}{7} = \frac{60}{x}$

c )
$\frac{6}{x} = \frac{14}{35}$

d )
$\frac{7}{6} = \frac{42}{x}$

e )
$\frac{2x}{3} = \frac{8}{6}$

f )
$\frac{2x}{15} = \frac{6}{9}$
g)

$\frac{5}{x + 4} = \frac{30}{54}$

h )
$\frac{6}{7} = \frac{3x}{28}$
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Answer 1

Explicação passo-a-passo:

a)

$\sf \dfrac{x}{5}=\dfrac{6}{10}$

$\sf 10x=5\cdot6$

$\sf 10x=30$

$\sf x=\dfrac{30}{10}$

$\sf \red{x=3}$

b)

$\sf \dfrac{3}{7}=\dfrac{60}{x}$

$\sf 3x=7\cdot60$

$\sf 3x=420$

$\sf x=\dfrac{420}{3}$

$\sf \red{x=140}$

c)

$\sf \dfrac{6}{x}=\dfrac{14}{35}$

$\sf 14x=6\cdot35$

$\sf 14x=210$

$\sf x=\dfrac{210}{14}$

$\sf \red{x=15}$

d)

$\sf \dfrac{7}{6}=\dfrac{42}{x}$

$\sf 7x=6\cdot42$

$\sf 7x=252$

$\sf x=\dfrac{252}{7}$

$\sf \red{x=36}$

e)

$\sf \dfrac{2x}{3}=\dfrac{8}{6}$

$\sf 6\cdot2x=3\cdot8$

$\sf 12x=24$

$\sf x=\dfrac{24}{12}$

$\sf \red{x=2}$

f)

$\sf \dfrac{2x}{15}=\dfrac{6}{9}$

$\sf 9\cdot2x=15\cdot6$

$\sf 18x=90$

$\sf x=\dfrac{90}{18}$

$\sf \red{x=5}$

g)

$\sf \dfrac{5}{x+4}=\dfrac{30}{54}$

$\sf 30\cdot(x+4)=5\cdot54$

$\sf 30x+120=270$

$\sf 30x=270-120$

$\sf 30x=150$

$\sf x=\dfrac{150}{30}$

$\sf \red{x=5}$

h)

$\sf \dfrac{6}{7}=\dfrac{3x}{28}$

$\sf 7\cdot3x=6\cdot28$

$\sf 21x=168$

$\sf x=\dfrac{168}{21}$

$\sf \red{x=8}$

Answer 2

Resposta:

a) 10x = 6×5 => × = 3.

b) 60×7 = 3x => x = 16.

c) 14x = 35 × 6 => x = 15.

d)42×6 = 7x => x = 36.

e)2x×6 = 3 × 8 => x = 2.

f)2x × 9 = 15 × 6 => x = 5.

g)30(x + 4) = 54 × 5 => 30x + 120 = 270

x = 150 / 30 == > x = 5.

h)28 × 6 = 7 × 3x => x = 8.