Can you solve Martin Gardner's "coin of the realm" puzzle?

Mark Frauenfelder 8:50 am Fri Apr 29, 2016

The Colossal Book of Short Puzzles and Problems is a 512-page collection of puzzles from the Martin Gardner's beloved Scientific American column. The easier puzzles are at the front of each section, and become more difficult as you progress. Here's one of the easy ones:

In the United States at least eight coins are required to make the sum of 99 cents: a half-dollar, a quarter, two dimes, and four pennies. Imagine yourself the leader of a small, newly independent nation. You have the task of setting up a system of coinage based on the cent as the smallest unit. Your objective is to issue the smallest number of different coins that will enable any value from 1 to 100 cents (inclusive) to be made with no more than two coins.

For example, the objective is easily met with 18 coins of the following values:

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90.

Can you do better? Every value must be obtainable either by one coin or as a sum of two coins. The two coins need not, of course, have different values.

A surprising solution to the (in)famous "Cross the Network" puzzle

My father introduced me to the "Cross the Network" puzzle when I was a kid. Here it is, as described by Martin Gardner in one of his early Mathematical Recreations… READ THE REST
My trip through the Starmaze: a world in the 9th dimension

There are times when I get tired of all of the major sites and apps that make up a lot of the seen Internet. Sadly, I was born too late… READ THE REST
Can you solve the "scrambled box tops" puzzle?

Here's a puzzle from Martin Gardner's Mathematical Games column, which ran for many years in Scientific American. I found it in his low-priced Dover edition anthology, My Best Mathematical and… READ THE REST
Short Post, just one paragraph

Dessert cheesecake wafer bear claw fruitcake. Fruitcake chupa chups donut candy canes marzipan. Apple pie sweet roll tart chocolate cake macaroon marshmallow carrot cake gummi bears sweet. Pastry sugar plum… READ THE REST
Save 50% on a 1-year subscription to Dashlane's premium password manager

We all know vital information about ourselves and our private digital accounts can be compromised by cybercriminals. However, many would be frightened to know just how compromised they and their… READ THE REST
The Bite Helper removes the itch of a mosquito bite in seconds

While mosquitoes have certainly earned their title as the deadliest animal on earth, their impact on most of our lives is usually a lot less consequential. But even though they… READ THE REST