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 water
upto a height of 6 cm. 20 spherical drops of oil of radius 9 mm are dropped
into it. What length of test tube
remains empty?.............tell me the solution to this problem or where the solution exists....

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someone with brains can do it....

Answers

2014-03-10T18:58:08+05:30
Diameter of the tube=3.6cm
⇒radius=1.8cm=18mm
total height=15cm=150mm
let height upto water=L=6cm=60mm
volume of 20 oil drops=20×(4/3)πr³
                               =20×4×9×9×9×22÷(7×3)
                               =80×729×22÷21
                               =61097.14286mm³
                               =61.09714286cm³
πr²h=61·9714286cm³
⇒h=6cm
⇒remaining height=15-(6+6)cm
=3cm
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