A glass paperweight is shaped like a right pyramid standing on a square base of side 12 cm, with a vertical height of 17.5 cm. What is its volume, in cubic cm?

A pyramid holds one third of the prism on the same base and of the same height: volume = (1/3) $x$ base area $x$ height = (1/3) $\times 12^{2}x17.5=48\times 17.5=840$ cubic cm. The trap $2520=144\times 17.5$ forgets the 1/3 and prices a square prism instead; 1260 uses 1/2 in place of 1/3, borrowing the triangle's formula; $70=(1/3)\times 12\times 17.5$ uses the SIDE of the base rather than its area.