Jackson Wan's answer to anonymous's Secondary 2 Maths Singapore question.

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Jackson Wan
Jackson Wan's answer
18 answers (Tutor Details)
1st
Sphere fits exactly in can -> means the radius of sphere = radius of the can.
let this radius be r, and diameter = 2r

Water just covers the sphere means the height of the water = height of the sphere = diameter

i) surface area of can in contact with water
= surf( base + curved surface)
= pi r^2 + 2 pi r (2r)

ii) Initial volume of water = Volume of cylinder(where h=2r) - volume of sphere = pi r^2 (2r) - 4/3 pi r^3
pi*r^2*(initial depth)= Initial volume of water solved above.
Solve for initial depth of water.