GeekDad Challenge of the Week Solution: Geeky Golf

Well, this week’s challenge turned out to be an embarrassment for me! As many of you pointed out, my example for scoring did not follow the correct order of operations or, as we lovingly refer to it, PEMDAS. 1 + 2 + 3 – 5 x 4 ÷ 2 != 2 when you use PEMDAS […]
Golf Balls

Well, this week's challenge turned out to be an embarrassment for me! As many of you pointed out, my example for scoring did not follow the correct order of operations or, as we lovingly refer to it, PEMDAS.

1 + 2 + 3 - 5 x 4 ÷ 2 != 2 when you use PEMDAS it equals:

  • 1 + 2 + 3 - 20÷ 2 =
  • 1 + 2 + 3 - 10 =
  • 6 - 10 =
  • -4

I hang my head in math shame for that one. Some of you pointed it out and then used the same left to right logic I used. Other people used PEMDAS like good little math geeks. I accepted both answers. Let's start with a recap of the puzzle:

This week's puzzle is similar to code golf but instead of code we'll use our good old friend arithmetic. How do you play Math Golf? Easy: Each of the main operations has a stroke value listed here:

  • Subtraction = 1 Stroke
  • Addition = 2 Strokes
  • Multiplication = 2 Strokes
  • Division = 3 Strokes

So this equation:

1 + 2 + 3 - 5 x 4 ÷ 2 = 2

Totals 10 strokes.
The challenge is to complete the following equation using the fewest strokes.

1 2 3 4 5 6 7 8 9 = 100

You can only use addition, subtraction, multiplication and division. You cannot rearrange the numbers: they must stay in the order they are given and you can't combine adjacent numbers to make a new number, for example 1 2 can't be made into 12.

As I already mentioned, I accepted both forms of answer, so this:

1 x 2 + 3 x4 x 5 - 6 + 7 + 8 - 9 = 100 (14 Strokes)

was accepted as well as the other variations. Now here's the part all the people who used PEMDAS are going to be happy with. If you use PEMDAS the shortest answer is ... wait for it:

1-2+3*4*5-6+7*8-9=100 (13 Strokes)

Yes, if you follow the rules like you're supposed to you get a shorter answer! That goes to show you PEMDAS is your friend -- embrace it!

Well, with all that out of the way, let's get to the winner of this little party! This week's challenge winner is Tim Hurst! Tim gets a $50.00 ThinkGeek gift certificate where he can spend it on lots of cool math geek stuff. Everyone else gets to save $10.00 of a $50.00 order at ThinkGeek by using this code: GEEKDAD44AF.

As for me, I'm going to write __ P__lease __E__xcuse __M__y __D__ear __A__unt __S__ally one hundred times so I never forget it again.