The weight Wkg of a metal bar varies jointly as it's length L and the square of it's diameter D mm. If W=140 when D =4 and L=54, find D interm of W and L

D =

Step-by-step explanation:

From the given question, the expression showing the relationship among the weight, length and diameter of the metal bar is;

W L

W = kL

where k is the constant of proportionality.

When W = 140, D = 4 and L = 54, then;

140 = k(54)

      = 864k

k =

  =

k =

⇒ W =

So that;

35L = 216W

=

D =

1/4 and 8/3 because:

the reciprocal if 4 is 1/4 because 4 is used as 4/1 and the opposite of that is 1/4. the opposite of 3/8 is 8/3 so that is the answer.