A rock is placed in a graduated cylinder to determine its volume. The following data are obtained. What is the volume of the rock?

Initial volume of water: 13.7 mL

Final volume of water: 28.9 mL

Easy

when rock is in water, it takes up a certain volume, say x

so

initial+x=final volume

luckily we have final and inital

13.7ml+x=28.9ml

minus 13.7ml both sides

x=15.2ml

the volme of the rock is 15.2ml