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Help 1

 Feb 20, 2018
 #1
avatar+7354 
+2

1)      w  and  t  vary inversely, so...

 

t  =  k / w

                               t = 1/5   when  w = 4  ,   so...

1/5  =  k / 4

                               Multiply both sides of the equation by  4

4 * (1/5)  =  k

 

4/5  =  k                  Now we can use this value of  k in the equation  w = k / t

 

t  =  (4/5) / w

                               Simplify.

t  =  (4/5) * (1/w)

 

t  =  4 / (5w)            To find t  when  w = 9 ,  plug in  9  for  w  in this equation.

 

t  =  4 / (5(9))

 

t  =  4 / 45

 Feb 20, 2018
 #2
avatar+7354 
+2

y  varies directly with  x  and inversely with  z .

 

y  =  kx / z

                            And  y = 18  when  x = 15  and  z = 5 .

18  =  k(15) / 5

                            Multiply both sides by  5 .

90  =  k(15)

                            Divide both sides by  15 .

6  =  k                  So...

 

y  =  6x / z

 

Find  y  when  x = 21  and  z = 7 .

 

y  =  6(21) / 7

 

y  =  126 / 7

 

y  =  18

 Feb 20, 2018

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