Calculating Cork Volumes for Amusement Park Water Slide

[tiz_07]

An amusement park is planning to build a water slide, and the park owners would like to use giant corks with density 0.28 g/cm^3 as "floats" for young children. What volume of cork is needed to keep 20% (by volume) of a 40 kg child above the water at the base of the slide (assuming the density of the child is 1.01 g/cm^3).

 

[Pyrrhus]

This is an Archimedes principle problem. What have you done?