Question 945422
If the box was solid,
{{{V[s]=20*15*10=3000}}}{{{cc}}}
Since it's not, subtract out the volume of the air space, by subtracting 1 cm from each side of each dimension.
{{{V[a]=18*13*8=1872}}}{{{cc}}}
So then,
{{{V=V[s]-V[a]=3000-1872=1128}}}{{{cc}}}
Convert the volume to cubic decimeters using,
{{{10}}}{{{cm}}}={{{1}}}{{{dm}}}
{{{10^3=1000}}}{{{cc}}}={{{1}}}{{{cd}}}
So then,
{{{1872(1/1000)=1.872}}}{{{cd}}}
And finally,
{{{m=rho*V}}}
{{{m=1(1.872)=1.872}}}{{{kg}}}