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Dan Rubin's SuperfluousBanter

Design, random musings, and the Web. Since 1977


Interview by Justin Goodlett (and win $20!)

Interview with Didier HilhorstI’m
excited to announce my
first ever interview
by Justin Goodlett of SkinnyJ.
Previous interviewees include Jon Hicks and Andy Arikawa — needless to
say I find myself in good company. I answer questions about design, aesthetics,
usability, Jakob Nielsen, inspiration and how I became to be a designer. Enjoy!

But wait…

There’s more! In the interview
I challenge readers to calculate my age using a mathematical formula. The first
reader to post a correct answer along with a rationale of the calculation in
the comments
will win a $20 gift certificate
from amazon.com. That’s as many dollars as necessary to buy a copy of
the new required reading by the folks at 37signals
entitled Defensive Design
— heck, you’ll even have enough left to grab a beer at your local

Update: There are some mucho smart and especially lightening fast people on the web. Damn. You’ve guessed it: the $20 gift certificate has been won, already. Congratulations to both Shaun and David for the answers. They both get $20. So, what did you think of the interview? Discuss!


This item was posted by dhilhorst on Tuesday, March 23rd, 2004.


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12 comments on “Interview by Justin Goodlett (and win $20!)”

  1. Posted by Bob on Tuesday, March 23rd, 2004.

    You’re 24.

  2. Posted by Bob on Tuesday, March 23rd, 2004.

    Oops, forgot the rationale:

    Because Google Calculator said so. ;-)

  3. Posted by Bob on Tuesday, March 23rd, 2004.

    Sheesh… one day I’ll learn to click on hyperlinks in order to post in the correct comments. I’m such a dumbass. Feel free to delete these comments. Or leave them up for the amusement of others. It’s your call. :-/

  4. Posted by David on Tuesday, March 23rd, 2004.

    54^7 = 1338925209984

    1338925209984 mod 65 = 24

  5. Posted by David on Tuesday, March 23rd, 2004.

    if that’s not enough detail:

    the ^ means the first raised to the power of second

    mod means the remainder when the first is divided by the second

  6. Posted by Didier Hilhorst on Tuesday, March 23rd, 2004.

    Very well done. Calculators make life easy. Now the hard part…

    Although you were all able to perform the calculation you didn’t provide me with a satisfactory rationale. I was expecting the calculation itself to be solved rather quickly.

    However I need an explanation of how modulo (mod) works and not just a description of the formula. Include a simple example along with a summary in words of how it is actually being calculated and the $20 is yours! But don’t forget to post it on SkinnyJ.

  7. Posted by waylman on Tuesday, March 23rd, 2004.

    Ok, that was a cool contest. Funny thing is I majored in math and even completed 2 semesters of calculous with the local community college in my last year of highschool, yet I don’t ever remember seeing ‘modulo’. Not that I didn’t, I just don’t remember. Of course it has been a few years since I used any of that stuff.

    Anyway, just wondering if there is a easy equation to find how anyones age would be respresented like that. I’m looking for a way to give my age (or anyones) and have it spit out the equation representing that age.

  8. Posted by James on Tuesday, March 23rd, 2004.

    [I thought I’d post this here too.]

    For a non-calculator solution (if anyone’s interested),

    If a (mod x) = b (mod x)

    and c (mod x) = d (mod x),

    then a*c (mod x) = b*d (mod x).

    Note also that negatives are permissible in modulo arithmetic, and any numbers with the same remainder in the corresponding base are equal (congruent). In other words,

    54 (mod 65) = -11 (mod 65).

    Continuing (all in mod 65),

    54^2 = (-11)^2 = 121 = -9

    54^4 = 54^2 * 54^2 = -9 * -9 = 81 = 16

    54^6 = 54^4 * 54^2 = 16 * -9 = -144 = -14

    54^7 = -14*-11 = 154 = 24

    Therefore, DH is 24.

  9. Posted by Didier Hilhorst on Tuesday, March 23rd, 2004.

    Some might think that stating my age with a mathematical formula is rather esoteric. But I thought it would be a nice challenge (it turned out to be to easy a challenge). So why modulo you ask? What’s so great about it?

    I find numbers fascinating. Prime numbers, Fibonacci sequence, Caesar cipher (simple shift cipher) and things alike. Cryptography plays an important role in technology security (online, offline and basically everywhere). Modulo aritchmetic is used in public key cryptography: RSA. Of course there’s much more to cryptography than just modulo arithmetic.

    I’d like to thank James for his non-calculator solution since it nicely shows how it works. I always use a simple example to explain how it works. Take 3^2(mod)2 for example.

    3^2(mod)2 = 9(mod)2

    2 * 4 = 8 (2 fits 4 times in 9)

    9 – 8 = 1 (which is the remainder)

    therefore: 3^2(mod)2 = 1

    I think this should be enough mathematics for a whole year. Back to important things! Back to design and interfaces!

  10. Posted by Jeff Minard on Tuesday, March 23rd, 2004.

    For furture reference, the easiest way to mark up Modulus is with a % sign. ie:

    2%1 == 1


    (3^2)%2 == 1

    In addition, modulus is really easy to figure out without a calculator. Simply subtract the modulus number until the reult is less than the modulus operator. This method seems a little easier than the one posted a few comments above by James. A few examples:

    9%2 = 1

    9-2 = 7 (7 < 2) { false }

    7-2 = 5 (5 < 2) { false }

    5-2 = 3 (3 < 2) { false }

    3-2 = 1 (1 < 2) { true }

    5%3 = 2

    5-3 = 2 (2 < 3) { true }

    7%2 = 1

    7-2 = 5

    5-2 = 3

    3-2 = 1

    19%4 = 3

    19-4 = 15

    15-4 = 11

    11-4 = 7

     7-4 = 3

    For a negative number, I imagine you can just drop the negative operator (work on it’s absolute value).

  11. Posted by Sunny on Tuesday, March 23rd, 2004.

    Didier – I am sure the figures are perfectly rounded!

  12. Posted by Goughe on Tuesday, July 27th, 2004.

    ooudfaqmhc bjaf.