Why do I get 0.31 for density change when atoms move farther apart?

[PhysicStud01]

Homework Statement

Homework Equations

Density = mass / volume

The Attempt at a Solution

the correct ans given is B.
Mass is constant. I calculated the volumes of each (the cube of the separation), found the difference in density and then divide the difference by the initial density. but the answer i obtained was 0.31, which is not even given here.
i verified my answer many times but there don't seem to be an error

 

[ehild]

Homework Statement

View attachment 81919

Homework Equations

Density = mass / volume

The Attempt at a Solution

the correct ans given is B.
Mass is constant. I calculated the volumes of each (the cube of the separation), found the difference in density and then divide the difference by the initial density. but the answer i obtained was 0.31, which is not even given here.
i verified my answer many times but there don't seem to be an error

You need the factor between the final density and the initial density,

 

[andrevdh]

Please show how you got to 0.31

 

[PhysicStud01]

You need the factor between the final density and the initial density,

thanks. now i got the answer.

it was much easier than i thought