Question

this was a question in class 10 maths paper for st georges school-alaknanda Q. A 15 cm long test tube having diameter of 3.6 cm has waterupto a height of 6 cm. 20 spherical drops of oil of radius 9 mm are droppedinto it. What length of test tuberemains empty?.............tell me the solution to this problem or where the solution exists....

Answer 1

area of cross section of the tube = π (3.6/2)² = π 3.24 cm²

Total volume of oil drops :  20 * (4/3) π 0.9³  cm³ = 19.44 π cm³

So the additional height that the oil drops will occupy on top of water already present :   volume / cross section area 
       = 19.44 / 3.24 = 6 cm

So total height of water + oil in the test tube :  6+6 cm
 Empty space height :  15 cm - 12 = 3 cm