# The value of y varies directly with x, and y=1 when x=2. What is y when x=4?

Apr 15, 2018

2

#### Explanation:

Here, $y \propto x$
$\Rightarrow y = k x$ where k is constant.
$\Rightarrow 1 = k .2$ [put y =1,x=2]
$\Rightarrow k = \frac{1}{2}$

Again, y = kx
rArr y = 1/2×4[put x = 4]
$\Rightarrow Y = 2$

Apr 15, 2018

$y = 2$

#### Explanation:

$\text{the initial statement is } y \propto x$

$\text{to convert to an equation multiply by k the constant}$
$\text{of variation}$

$\Rightarrow y = k x$

$\text{to find k use the given condition}$

$y = 1 \text{ when } x = 2$

$y = k x \Rightarrow k = \frac{y}{x} = \frac{1}{2}$

$\text{equation is } \textcolor{red}{\overline{\underline{| \textcolor{w h i t e}{\frac{2}{2}} \textcolor{b l a c k}{y = \frac{1}{2} x} \textcolor{w h i t e}{\frac{2}{2}} |}}}$

$\text{when "x=4" then}$

$y = \frac{1}{2} \times 4 = 2$