Question
A glass beaker having mass 390 g and an interior volume of 500 cm^{3} floats on water when it is less than half filled with water. What is the density of the material of the beaker?

3.20 g/cc

2.79 g/cc

3.50 g/cc

None of these
medium
Solution
2.79 g/cc
As the beaker floats in water when less than half filled with water, it will float just fully submerged when half filled. In this situation, mass of beaker + mass of water in it
i.e., outer volume of beaker
Now as inner volume of beaker is given to be 500 cc, so the volume of the material of beaker = 640 – 500 = 140 cc. But as mass of beaker is 390 g, so density of material of beaker
= 2.79 g/cc
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