An inversely proportional equation for our set of circumstances looks like this:

. We have a t value of 2 and an r value of 30, so we will sub those values in and solve for k, the constant of variation.

. Multiply both sides by 30 to get that k = 60. Now we need to find t when r = 50. We can do this now because we have a value for k.

and t = 1.2 hours.