If all of that energy were supplied by the estimated TOTAL reserves of coal (25000 Quads), petroleum (6000 Quads), and natural gas (6000 Quads), then how many years would ALL of these reserves last?

Question

anonymous · Answer

This was the first part of the question:
Assume that world energy consumption is about 500 Quads each year (~ 5x1020 J). If all of that energy were supplied by the estimated 5000 Quads of natural gas reserves, then how many years would these reserves last?