This stack is made of 2 cm cubes glued together. What is the total surface area of the stack, including the base it stands on?

Count the squares seen from each of the six directions: 5 from above, 5 from below, 5 from the front, 5 from the back, 5 from each side: 30 squares. Each is $2\times 2=4{\text{ cm}}^2$, so $30\times 4=120{\text{ cm}}^2$. (100 leaves out the base; 192 is $8\times 6\times 4$, forgetting that glued faces are hidden.)