水的体积=0.2÷(1×10³)=0.2立方分米;
所以石头总体积=0.3-0.2=0,1立方分米;
每块石头体积=0.1÷25=0.004立方分米;
密度=0.01÷0.004÷1000=2.5×10³千克/立方米;