If y varies directly with x, how do you find y when x = 3 if y = -3 when x =6?

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Answer 1 · 2017-05-17T08:59:06

$y = -3/2$

We can write direct variation in maths as:

$y prop x" "$ Make an equation by using a constant ( $k$ )

$y = k xx x" "$ Find the value of $k$

$y/x = k" "$ Use the pair of values given $x=6 and y=-3$

$k =-3/6$

$k=-1/2" "$ use this and the given $x$ value to find $y$

$y = -1/2 xx 3$

$y = -3/2$

You can also write a direct proportion as equivalent fractions:

$x/y = (6)/-3 = 3/y" "$ now cross multiply

$6y = -3 xx3$

$y = (-3xx3)/6$

$y = -9/6 = -3/2$