Final answer:
To measure the volume of 15 thumb tacks, use a graduated cylinder and water displacement. Subtract the initial water volume from the volume after adding the tacks to find their combined volume.
Step-by-step explanation:
To measure the volume of 15 thumb tacks, the most appropriate method would be to use water displacement in a graduated cylinder. First, fill the graduated cylinder with water to a certain level, and record the volume. Then, carefully add the thumb tacks to the cylinder, ensuring not to splash any water out. The difference in water levels before and after the addition of thumb tacks is the combined volume of the 15 thumb tacks.
This method is based on Archimedes' principle, which states that the volume of the displaced fluid is equal to the volume of the object submerged. This is particularly useful when dealing with irregularly shaped objects like thumb tacks, where using a ruler wouldn't be feasible.