Since we have TWO halves at either end,adding them will give us 1 complete sphere.
So now we have to find the volume of a sphere+volume of a cylinder.
Volume of a sphere is given by (4/3)x(pi)x(r^3)
Volume of a cylinder is given by (pi)x(r^2)x(h).
(Since diameter is given as 40cms and we know Diameter=2xRadius =>Radius r=20cms)
The ladder problem can be solved by using Pythagoras' Theorem which states that if a and b be the sides of a right angled triangle, the the third side(hypotenuse) is given by the root of sum of squares of the other sides i.e. if C is the hypotenuse then c^2 = a^2 + b^2
You have to solve for (15)^2 = 7^2 + b^2