Question

Utilizando a multiplicação em cruz,resolva estas equações :
A) x/6 = 14/21
B) x/9=18/27
C)12/x=3/7
D)15/2=90/x

Answer 1

a)
x = 14      21x = 14 * 6   ------> 21x = 84 ----->  x = 84 : 21 ----> x = 4      
6     21

b)
x  =  18  ------>  27x = 18 * 9 -----> 27x = 162  ----> x = 162 : 27  ----> x = 6
9       27

c) 
12  = 3  -----> 3x = 12 * 7  -----> 3x = 84  ----> x = 84 : 3  ----> x = 28
x      7

d)
15   =  90  ------> 15x = 90 * 2  -----> 15x = 180  -----> x = 180 : 15  ----> x = 12   
 2         x

Answer 2

a)$\frac{x}{6}= \frac{14}{21}$

$21x=84$
$x= \frac{84}{21}$

$x=4$

b) $\frac{x}{9}= \frac{18}{27}$

$27x= 162$
$x= \frac{162}{27}$

$x=6$

c)$\frac{12}{x} = \frac{3}{7}$

$3x=84$
$x= \frac{84}{3}$

$x=28$

d)$\frac{15}{2} = \frac{90}{x}$

$15x=180$
$x= \frac{180}{15}$

$x=12$