Question

1) Calcule as porcentagens :

a) 3% de 90.
b) 15% de 120.
c) 180% de 20.

2) Sendo x = 8 e y = -10,calcule as expressões algébricas :

a) 5x + 3y =
b) y - x =
3) Calcule as proporções :

a) 8/9 = x/27
b) 5/10b= 15/x
c) 2/6b= x/24
d) 12/15 = x/45
e) 7/28= 14/x

Answer 1

Explicação passo-a-passo:

1)

a) 3% de 90

3/100 de 90= 3*90/100=

270/100 = 2,7

b)15% de 120

15/100 de 120= 15*120/100=

1800/100=18

c)180% de 20

180/100 de 20= 180*20/100=

3600/100=36

2)

x=8 e y= -10

a)5x+3y=

5*8+3*(-10)

40 - 30 = 10

b)y-x

(-10)-(+8)=

-10-8= -18

3)

a) 8/9=x/27

9x=8*27

9x=216

x=216/9

x=24

b) 5/10=15/x

5x=10*15

5x= 150

x= 150/5

x= 30

c)2/6=x/24

6x=2*24

6x=48

x=48/6

x=8

d)12/15=x/45

15x=12*45

15x=540

x=540/15

x=36

e)7/28=14/x

7x=28*14

7x=392

x=392/7

x=56