Question

Use k as the constant of proportionality to write the equation expressing the relationship: y varies inversely as x. if y = 10 when x = 5, determine k.

Answer 1

For an inverse relationship of the form 
$y= \dfrac{k}{x}$
you can solve for k, the constant of variation (or proportionality), by multiply both sides of the function to get $xy=k$. Substituting 5 for x and 10 for y, you see that k = 50.