Paying with coins
Task number: 2800
Show that every integral sum greater than or equal to 8 crowns can be paid with 5-crown and/or 3-crown coins.
\(8=3+5\), \(9=3+3+3\), \(10=5+5\). For \(n\ge 11\) we use the inductive assumption that it is possible to pay \(n-3\), and we add one 3-crown coin.