Question

Given that y varies directly with x, and y = 15 when x = 8 , what is the proportionality constant, k? Round your answer to the hundredths place.

Answer 1

The proportionality constant "k" is 1.88

Solution:

Given that y varies directly with x

y = 15 when x = 8

To find: proportionality constant "k"

Direct variation means that increase/decrease in one quantity also causes increase/decrease in other quantity.

⇒ y varies directly with x

This means,

$y \propto x$

Can also be written as:

y = kx

Where "k" is the proportionality constant

Substituting the given values of "x" and "y"

15 = k(8)

$k = \frac{15}{8}$

k = 1.875

On rounding to nearest hundredths place we get 1.88

Thus the proportionality constant is 1.88