Take a board with 64 squares on it. Put a grain of wheat on the first square--two on the second--four on the third. Keep doubling in this manner and you will find there isn't enough wheat in the world to fill the sixty-fourth square. It can be the same with compound interest.
A gem of short story in the form of correspondence between the leaders of two opposing Political Blocs whose escalation of hostilities is rapidly suppressed from a surprise third party.
An old woman comes to Mars because a fraudulent travel agent offers a "trip to heaven". She and other members of her traveling group find an extremely battered and derelict rocket which was supposed to be used for the last part of the trip. And it is used for that trip, in a pretty literal sense.
After some sudden and unspecified catastrophe has depopulated England, the countryside reverts to nature, and the few survivors to a quasi-medieval way of life. The first part, The Relapse into Barbarism, is the account by some later historian of the fall of civilisation and its consequences, with a loving description of nature reclaiming England. The second part, Wild England, is an adventure set many years later in the wild landscape and society.