Solve the empty gas tank of a truck needs to be completely filled. the tank is shaped like a cylinder that is 3.5 ft long with a diameter of 2.2 ft . suppose gas is poured into the tank at a rate of 2.5 ft3 per minute. how many minutes does it take to fill the empty tank

5.3 minutes.  
First, let's calculate the volume of the tank. That will be the area of the base multiplied by it's length. And since it's base is a circle, the area is pi*r^2. So:
 V = l*pi*r^2
 V = 3.5 * pi * (2.2/2)^2
 V = 3.5 * pi * (1.1)^2
 V = 3.5 * pi * 1.21
 V = 4.235 * pi
 V = 13.30464489
 
 So the tank has a volume of about 13.3 ft^3. Now simply divide that volume
by the rate of incoming fluid. So
 13.3 / 2.5 = 5.32 
 Rounding to 2 significant figures gives a time of 5.3 minutes.