MathDB

6

Part of 1974 Canada National Olympiad

Problems(1)

Stamps

Source: Canada 1974/6

1/13/2007
An unlimited supply of 8-cent and 15-cent stamps is available. Some amounts of postage cannot be made up exactly, e.g., 7 cents, 29 cents. What is the largest unattainable amount, i.e., the amount, say nn, of postage which is unattainable while all amounts larger than nn are attainable? (Justify your answer.)