Step-by-step explanation:
Density is defined as the amount of mass present in per unit volume of a substance.
Mathematically, Density =

Since, density is directly proportional to mass. Hence, when we increase the mass then there will be increase in the density of material. But when we decrease the mass of a material the its density will decrease.
On the other hand, density is inversely proportional to volume. Therefore, an increase in volume of a material will lead to a decrease in its density.
Thus, we can conclude that following sentences describe how the scientist can lower the material’s density.
- The scientist can decrease the mass while keeping the volume constant.
- The scientist can increase the volume while keeping the mass constant.