Rational expression word problem

Question

A large mixing tank currently contains 200 gallons

of water, into which 10 pounds of sugar have been

mixed. A tap will open, pouring 10 gallons of water

per minute into the tank at the same time sugar

is poured into the tank at a rate of 3 pounds per

minute. Find the concentration (pounds per gallon)

of sugar in the tank after t minutes.

Answer 1

Concentration = pounds of sugar / gallons of water

pounds of sugar (at time t) = 10 + 3t

gallons of water (at time t) = 200 + 10t

So the concentration at any time t, let's call it C(t), can be written as:

C(t) = (10 + 3t)/(200 + 10t)