# How to guess the mystery number in guessing games

So, a friend just challenged you to think of a number between 1 and 1000, huh? Well, here's a simple way to guess the number without guessing random numbers.

Thanks to chooseausername for giving me the game
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## Step 1: Half of what?

Ok, so your number is big. Like, big as 1000. Well, you don't just guess a random number. You say the number that's half of 1000. Well, how do you figure that out? You shrink the number down, of course! Take the numbers after the second digit down, leaving you with 10. Whats half of 10? 5, of course! After that, add the zeros you took off the 10 to the 5, making it 500.

## Step 2: What if the number is wrong?

Ok, so 500 was wrong. That is to be expected, though. In this case the number is greater, so you have to know what's half of 500 and add it. If the number was lesser, you'd just have to know what's half of 500 and guess from there. So, half of 500 is 250. Then you add 250 to 500, which is 750.

## Step 3: Still wrong?

Ok, so the number is lower. You can't divide the number by half because it's greater than 500. So, you must go down by 50, making the number 700.

## Step 4: Narrow it down...

Now, we know the number is greater than 700, but less than 750. So, you guess half of 50 plus 700 which is 725. However, the number is lower, so we guess 5 down, which is 720. The number is still wrong, so we go 10 down, making the number 710. The number was correct, but if it wasn't, it would tell you if it was greater or less, so you would add or subtract 5, and work from there. This time, I only had to guess 5 times, which is a record, but it may take up to 15 tries if you use this method.

Oh, if you want to practice this method, you can play it here.

Thanks for viewing!
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tech-king6 years ago
i won! beat this: I'm thinking about a number between 0 and 1000. Try to guess it ! You said : 500? My number is lower ! You said : 243? Congratulations ! You won ! You found my secret number in 1 tries. Your score is : 1000 (Press Reset to start a new game.)
coolz (author)  tech-king6 years ago
prove it! post a picture
6 years ago
will do.
coolz (author)  tech-king6 years ago
ok. but someone beat that already. you cant beat him because he got the maximum score already
6 years ago
what if i hack?
coolz (author)  tech-king6 years ago
1. that will get you disqualified 2. hacking wont help
6 years ago
it helps! type this into address bar: javascript:alert(random_number); works in firefox and konqueror.
6 years ago
I'm thinking about a number between 0 and 1000. Try to guess it ! ---> javascript:alert(random_number); <--- ---> new window opens: 656 <--- You said : 656? Congratulations ! You won ! You found my secret number in 0 tries. Your score is : Infinity (Press Reset to start a new game.)
tech-king6 years ago
game didnt work! it wouldnt display fractions, decimals or exponents. I'm thinking about a number between 0 and 1000. Try to guess it ! You said : NaN? You said : NaN? You said : NaN? You said : NaN? You said : NaN? You said : NaN? You said : NaN? You said : NaN? You said : NaN? You said : NaN? You said : NaN? You said : NaN? You said : NaN? You said : NaN? You said : NaN?
coolz (author)  tech-king6 years ago
its not supposed to display those things
6 years ago
you mean it wont do fractions, exponents, roots, algebra or basic expressions? lowzy game.
coolz (author)  tech-king6 years ago
no, its a game, not a homework machine
6 years ago
its not a smart program.
coolz (author)  tech-king6 years ago
6 years ago
i know a neuronal net coded in html!
6 years ago
thus its a dumb program. it should freeze up at math.
coolz (author)  tech-king6 years ago
its a game
6 years ago
and a dumb one at that
coolz (author)  tech-king6 years ago
i didnt even make the game! if you're gonna complain, complain to chooseausername
zimmemic256 years ago
i needed 10 tries. the ****ing number was 559!!! how should someone guess it??? LOG: I'm thinking about a number between 0 and 1000. Try to guess it ! You said : 500? My number is greater ! You said : 750? My number is lower ! You said : 700? My number is lower ! You said : 600? My number is lower ! You said : 550? My number is greater ! You said : 560? My number is lower ! You said : 555? My number is greater ! You said : 556? My number is greater ! You said : 557? My number is greater ! You said : 558? My number is greater ! You said : 559? Congratulations ! You won ! You found my secret number in 10 tries. Your score is : 100
n8man6 years ago
Coolz really left!
mrmucox6 years ago
I win!
coolz (author)  mrmucox6 years ago

## NEW RECORD HOLDER!

congrats! you have the record forever because that was the maximum possible score!
6 years ago
Looks like he hacked look at the one of the person who hacked.
6 years ago
Ummm... no. You'll notice it's 500, my first guess. Anyone's first guess.
6 years ago
I just said that because I lost. No hard feelings.
Keith-Kid6 years ago
Haha!
coolz (author)  Keith-Kid6 years ago
(removed by author or community request)
6 years ago
Huh???
coolz (author)  Keith-Kid6 years ago
can you beat my record?
6 years ago
I tied it.
coolz (author)  n8man6 years ago
yes, but i have it because i was first
6 years ago
I did mine at 3:43 P.M. PST. When did you do yours?
coolz (author)  n8man6 years ago
I set the record on the day i made this instructable! i beat you by 2 days!
6 years ago
Ok you win. I agree with you on Skate
coolz (author)  n8man6 years ago
nope. this guy called mrmucox got the record...
n8man6 years ago
What is your highest score, mine is 200. (on my second try) You also have it wrong at the third step. You divide the difference of the higher and lower number and add/ subtract it to the last number you guessed and continue doing that until you get the number choosing either the higher or lower when the difference is odd. Good instructable though, it displays the best way to crack this puzzle.
gamer6 years ago
Where is the link to the game??! Very nice technique, but if would be nice to have a link to the game. Thanks. -gamer
coolz (author)  gamer6 years ago