1. The problem statement, all variables and given/known data A hemispherical piece of ore of radius a contains flakes of gold. The flat base of the ore is in the x, y plane and its curved surface is in the region z > 0, where x, y, z are cartesian co-ordinates with origin at the centre of the base. The gold density is kz kg m−3, where k is a constant. What is the total mass of gold in the ore? 2. Relevant equations 3. The attempt at a solution Using multiple integrals I got an answer of (pika4)/4 kg. Can someone please check if this is the correct answer. Thanks a lot. A simple yes or no will do.