# maths

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

• maths -

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 -

eh? inversely ==> xy = k

8*18 = k
k = 144

when y=16,
x*16 = 144
x = 9

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