Question

If y varies inversely as x and y is 2.5 when x is 6, what is y when x is 4? a. 3.75 b. 1.67 c. 0.1 d. 7.5 Please select the best answer from the choices provided

Answer 1

Because y varies inversely as x, therefore
$y= \frac{k}{x}$
where k =  constant.

When x = 6, y = 2.5. Ther efore
$\frac{k}{6} = 2.5$
Cross multiply.
k = 6 x 2.5 = 15

The equation is
$y = \frac{15}{x}$

When x = 4, obtain
$y = \frac{15}{4}= 3.75$

Answer: a. 3.75

Answer 2

Inverse proportion is given in the form
$y= \frac{k}{x}$

We need to work out the constant, k, by substituting x = 6 and y = 2.5
$2.5= \frac{k}{6}$
$k=2.5*6$
$k=15$

The value of y when x = 4
$y = \frac{15}{x}$
$y= \frac{15}{4}$
$y=3.75$