The diagram shows three steps in an experiment to measure the density of a metal rod.
One has to simply remember the formula of density in order to solve this question.
Density is defined as mass per unit volume
in this case, mass is 280g , and volume is 40cm^3
Hence, density= 280/40=7g/cm^3
Add on: It might be worthwhile to note that
Higher density objects will sink while low density object floats.
Find the density of sand, with only the information given below. Note that density of water is 1g/cm^3 and that the beakers are identical and filled to the brim . ( FIG 1.2)
Science Tuition Singapore 