You are going to purchase $100 worth of gasoline for your boat. if gasoline is selling for $0.75/l and the density of gasoline is 0.750 kg/l, how much will the gasoline weigh?

In this problem, we need:

   (1 gallon)=(6 pounds)      or     1 = (

   (1 quart)=(1/4 gallon)      or     (4 quarts)=(1 gallon)    or    1 = (

   (16 ounces)=(1 pound)     or    1 =

We have:

       1 quart

      (1 quart)*1

    (1 quart)*((1 gallon)/(4 quarts))

    (1 quart)*((1 gallon)/(4 quarts))*((6 pounds)/(1 gallon))*((16 ounces)/(1 pound))

   (1)*(1/4)*(6/1)*(16/1)   ounces       [note: gallons, quarts, pounds all cancel out]

       24 ounces

Checking:  If a gallon weighs 6 pounds, a quart weighs 1.5 pounds  [that is, 6/4].

     That's 24 [that is, 1.5*16] ounces.  Yes.