Posted by **Jay** on Friday, March 30, 2012 at 10:54pm.

z varies directly as x^2. If z=36 when x=3,find zwhen x=4.

- algebra -
**Reiny**, Saturday, March 31, 2012 at 7:57am
z varies directly as x^2 -----> z = kx^2 , where k is a constant

if z=36, x = 3

336 = k(9)

k = 4

so y = 4x^2

when x=4 , y = 4(16) = 64

or , by ratio ....

z1/z2 = x1^2/x2^2

z1/36 = 4^2/3^2

z1 = 36(16/9) = 64

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