Question

Y varies inversely with x. If y=6 when x=-4, find y when x=3

Answer 1

y = -8

Explanation:

When two variables vary inversely, their relation is proportional. This means that their product is constant.

We can show the constant of proportionality (k) using the equation:

x · y = k

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Note: you may also see this written as:

y = k / x

⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯

↓ plugging in the given values

(-4) · 6 = k

-24 = k

k = -24

Using this constant, we now solve for y when x = 3 by plugging that value into the proportionality equation above:

x · y = k

↓ plugging in the known values

3 · y = -24

↓ dividing both sides by 3

y = -24/3

y = -8