While researching the suspects you hear a rumor that some of Fluffy's medicine is missing.  You talk to Miss Helper and ask her questions about the amount of medicine Fluffy was supposed to take.  She is happy to answer questions and tells you a lot of good information.

            She says that the medicine is in liquid form and is supposed to be mixed into Fluffy's water.  She says that Fluffy's water already has a 5% mixture in it when they give it to her.  She says they always mix in a little medicine for all the elephants to help them stay healthy.  She just needs to add enough medicine to raise the level of medicine from 5% to 15%.  If there is too much medicine, Fluffy will get sick from it; not enough medicine and Fluffy won't get better.

            You can see that this is a Weighted Averages problem, but what you can't see right away is if Miss Helper has been using the correct amount of medicine.  There is 29.4 gallons of medicine missing.  Has she been taking medicine home so she can keep Fluffy there, or has she been using the correct amount the entire time?  Let's see:

How many gallons of medicine should she have poured into Fluffy's water if Fluffy has 250 gallons of water already?  Remember, the medicine needs to make up 15% of the water/medicine mixture. (Click on the Weighted Averages button for help with solving weighted average problems.)

Is the correct amount missing?