If Y varies inversely as twice x and when x = 3, y = 8 how do you find y when x = 2?

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Answer 1 · 2017-05-29T13:42:58

When $x = 2, y = 12$ $x=2, y = 12$

Write the statement as an inverse proportion first:
$y \propto \frac{1}{2 x}$ $y prop 1/(2x)$
Change to an equation using a constant $k$ $k$

$y = \frac{k}{2 x},$ $y = k/(2x)," "$ which can be written as $k = 2 x \times y$ $" "k = 2x xx y$

Use the values given to find a value for $k$ $k$
$k = (2 \times 3) \times 8 = 48$ $k = (2xx3) xx8 = 48$
Use the values for $k and x$ $k and x$ to find $y$ $y$ .

$y = \frac{k}{2 x} = \frac{48}{2 \times 2}$ $y = k/(2x) = 48/(2xx2)$

$= \frac{48}{4} = 12$ $= 48/4 = 12$

Answer 2 · 2017-05-29T13:50:14

y = 12

Here $y \propto \frac{1}{2 x}$ $y prop 1/(2x)$

or, $y = k . \frac{1}{2 x}$ $y = k. 1/(2x)$ ..............(i)

put x = 3 & y = 8 we get, $8 = k . \frac{1}{2 \times 3}$ $8 = k. 1/(2xx3)$

$\Rightarrow k = 48$ $rArr k = 48$

Again putting the value of k & x in (i) to find 'y'

$\Rightarrow y = 48 . \frac{1}{2 \times 2}$ $rArr y = 48. 1/(2xx2)$

$\Rightarrow y = 12$ $rArr y = 12$