»  Solutions to puzzles in my VDARE.com monthly Diary

  December 2016


My December diary included the following brainteaser

I found pennies, nickels and dimes for a total of 18 coins. The total monetary value was 73 cents. How many of each denomination did I find?


• Solution

I noted that: "As usual in math there is an elegant solution and a merely enumerative one." This is true; but as one reader pointed out, the elegant solution is actually longer than the rock-breaking one.

Writing them out on the page here, in fact, I'm not sure which is which.

The odd 3 cents have to be pennies. Any further pennies must come in fives. So there can be

The first and last don't work because 15 nickels > 70 cents while 5 dimes < 60 cents. So there are 8 pennies.

That leaves 65 cents in ten other coins. That means an odd number of nickels.

One nickel … no. Three nickels … no. Five nickels … no. Seven nickels … there you go, 7 nickels and three dimes.