Posted by **tuhituhi** on Tuesday, January 29, 2013 at 7:46am.

if x and y vary inversely and x=18 when y=8,find x when y=16

- maths -
**Reiny**, Tuesday, January 29, 2013 at 7:55am
x and y vary inversely ---y = kx , where k is a constant

given: x=18, y = 8

8 = 18k

k = 4/9

so y = (4/9)x or 9x = 4y

when y = 16

9x = 4(16)

x = 64/9

or

x1/y1 = y2/x2

18/8 = 16/x2

18x2 = 8(16)

x2 = 8(16)/18 = 64/9

- maths -
**Steve**, Tuesday, January 29, 2013 at 10:34am
eh? inversely ==> xy = k

8*18 = k

k = 144

when y=16,

x*16 = 144

x = 9

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