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. Â For everyone else the answer is after the break….

Move the ‘2’ up half a line to make 101 – 10^{2}Â = 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.

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I had this one…

I thought it was similar to the matches puzzle:

101=102-1

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.

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

I think it’s time you took off your mask to reveal the underlying twit.

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

Also got 101=102-1

I too….

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.

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.

Silly wireless keyboard missed an “h” in the last sentence (should be Three x Three)

Brilliant solution.

like ðŸ™‚

Ingenious. Great answer, safc4ever!

(I got the ‘real’ answer but I prefer this one!)

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!

I love this answer!

Yes, I did get it right despite thinking the answer was a bit sneaky.

I got a different base-3 solution: 110-102=1

In base-10 that is 12-11=1

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

Thats wrong. 101-102 Mod2= -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.

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”.)

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·¢¼þÈË: “Richard Wiseman”

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Ö÷Ìâ: [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”

I had a different answer, but kinda like that. This was a good one.

I’d seen the puzzle before and still didn’t get it.

Es genial… Muy interesante ðŸ˜€

TambiÃ©n, Â¿puede ser?

101=102-1

Less than a minute

-101+102=1

By moving my right index finger just so, I got

1 = 1

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101-10^2=1 All you need is to move up the 2 of 102 a little bit to make 102 be 10^2.

and what about this 65-43=21 move 2 number to make this equation true.?

and what about this 65-43=21 move 2 numbers to make this equation true.

Can’t do the correct notation but the answer is: 65 – 4 cubed = 1 base 2