coverOn Friday I posted this puzzle….

Can you move just one digit and make the following equation correct:

101 – 102 = 1

If you have not tried to solve it, have a go now.  For everyone else the answer is after the break….

Move the ‘2’ up half a line to make 101 – 102 = 1

Any other solutions?

I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here). You can try 101 of the puzzles for free here.

39 comments

  1. I got 101-102=1 turns into 101=102-1 by moving one of the lines in the equals sign. But to be fair he did say digits.

    1. It’s a bit weasley, but you could claim that the top bar of the equals sign is the digit “1” on its side.

    2. That was my solution that I didn’t think was the ‘correct’ one, except I used the bottom line of the equals sign, and pretended it was a match ‘1’. Stupidly after I’d commented on this on Friday I then re-read the comments and was hit by the spoiler

  2. It doesn’t have to be Denary ie Base 10…

    In base 3, move the 2 to in front of the 1 on the right hand side:

    101 – 10 = 21 (Ten minus Three equals Seven)

    In case anyone is unfamiliar with number Bases, each digit to the left is n times the value of the digit to its right, with the right-most digit always being “One”, “n” is the Base number (Base n). in Base Ten, 10 is Ten and 100 is Ten x Ten (One Hundred) etc. In Base 3, 10 is Three and 100 is Tree x Three (Nine) etc.

    1. I think yours is the best answer. I get Richard’s answer but in his solution it is clear that the font size is smaller as well. In your elegant solution, which I must read again to understand base 3, one digit is simply moved and nothing else.

    2. Yow! Thank goodness that someone else came up with the number bases so that I didn’t have to post on it!!! Thank you, safc4ever!

  3. 101 – 102 ≡ 1 without doing anything if you compute the answer in modulo 2 arithmetic. That is 101 ≡ 1 (mod 2), 102 ≡ 0 (mod2) , and 1 ≡ 1 (mod 2). Thus 101 – 102 ≡ 1 (mod 2). Math nerd? Yes, I suppose.

    1. In response to Anonymous, typically the mathematical definition of a mod requires that the result be non-negative, in which case -1(mod2) = 1.

  4. Nope, didn’t get it, despite some ten minutes of puzzling. I like it; good puzzle.

    (The matchstick solution did occur to me, but I’d have been disappointed if it were the correct answer given the term “digit”.)

  5. ҿֵѧⱾ飬ҲԸɵ飬ĿʼдʲôdzǸտİ档—————— ԭʼʼ ——————
    : “Richard Wiseman”
    ʱ: 2014310(һ) 4:31
    ռ: “1250493584”;
    : [New post] Answer to the Friday Puzzle..

    Richard Wiseman posted: “On Friday I posted this puzzle…. Can you move just one digit and make the following equation correct: 101 – 102 = 1 If you have not tried to solve it, have a go now. ?For everyone else the answer is after the break…. Move the ‘2’ up ha”

  6. Anything you consume will be left with your stomach regardless
    of whether you prefer it to or not. Again, you have to consider everything, surgery, medication, v3 diet, exercise, most of those factors
    enter into play.

    Being a stimulant, it affects the CNS or the central nervous system as well.
    Before taking any type of v3 weight loss supplement
    you will want to see your doctor. that guy

  7. Right here is the perfect web site for anyone who wants
    to find out about this topic. You realize so much its almost tough to argue
    with you (not that I really would want to…HaHa). You certainly put a brand new spin on a subject that has been written about for many years.
    Wonderful stuff, just great!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

w

Connecting to %s