If y varies directly with x, and if x = 7.5 when y = 10, how do you find x when y = 4?

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Answer 1 · 2018-05-27T23:24:41

$x = 3$ $x = 3$

$y$ $y$ varies directly with $x$ $x$

$y \propto x$ $y ∝ x$

$y = k x$ $y = kx$

Where $k$ $k$ is proportionality constant

If $x = 7.5$ $x = 7.5$ then $y = 10$ $y = 10$

$k = \frac{y}{x} = \frac{10}{7.5} = \frac{4}{3}$ $k = y/x = 10/7.5 = 4/3$

When $y = 4$ $y = 4$

$x = y/k = 4/(4/3) = cancel(4) × 3/cancel(4) = 3$