Newest questions tagged cops-and-robbers - Puzzling Stack Exchange most recent 30 from puzzling.stackexchange.com 2019-11-20T12:55:52Z https://puzzling.stackexchange.com/feeds/tag?tagnames=cops-and-robbers&sort=newest https://creativecommons.org/licenses/by-sa/4.0/rdf https://puzzling.stackexchange.com/q/50261 0 Robbers - Make 24 [closed] theonlygusti https://puzzling.stackexchange.com/users/21469 2017-03-22T15:58:09Z 2017-03-23T07:50:22Z <p>The make-24 puzzle is an oldie, but a very fun one at that.</p> <blockquote> <p>Given four different numbers, produce—through a sequence of operations upon only those four numbers—the number twenty-four.</p> </blockquote> <p>For example, given $2,2,3,8$ you can make $24$ by: $2\times 3\times\frac82$.</p> <p>Note that each of the given numbers must be used exactly one time in the solution, and no other digits may appear anywhere.</p> <hr> <p>This question is for the robbers to submit solutions to the problems posed by the cops.</p> <p>The <a href="https://puzzling.stackexchange.com/questions/50259/coppers-make-24">cops' thread</a> should contain posts which specify the</p> <ul> <li>four numbers you are allowed to use</li> <li>operations you are allowed to use</li> </ul> <p>Have a look at the problems people have submitted <a href="https://puzzling.stackexchange.com/questions/50259/coppers-make-24">on the cops' thread</a> and see if you can solve any of them. If you do manage to solve any, show it off here!</p> <p>Make sure that your answer contains a link back to the problem's post, you can get the url by clicking the "share" link at the bottom of an answer.</p> <p><a href="https://i.stack.imgur.com/RMlbL.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RMlbL.png" alt="share a link to this answer"></a></p> <p>So, your answers should be somewhat modelled like:</p> <blockquote> <p>I had a lot of fun solving Chris' problem! Here's his post: <a href="https://puzzling.stackexchange.com/a/404">https://puzzling.stackexchange.com/a/404</a>. I can use plus, minus, divide, multiplication, square roots and factorials to get $24$ from $3,8,12,50$ and I finally did it!</p> <p>And my solution:</p> </blockquote> https://puzzling.stackexchange.com/q/50259 -1 Coppers - Make 24 [closed] theonlygusti https://puzzling.stackexchange.com/users/21469 2017-03-22T15:54:55Z 2017-03-22T16:31:44Z <p>The make-24 puzzle is an oldie, but a very fun one at that.</p> <blockquote> <p>Given four different numbers, produce—through a sequence of operations upon only those four numbers—the number twenty-four.</p> </blockquote> <p>For example, given $2,2,3,8$ you can make $24$ by: $2\times 3\times\frac82$.</p> <p>Note that each of the given numbers must be used exactly one time each in the solution, and no other digits may appear anywhere.</p> <hr> <p>Here cops can submit puzzles for <a href="https://puzzling.stackexchange.com/questions/50261/robbers-make-24">the robbers</a> to solve!</p> <p>As a cop, your job is to create a specific make-24 problem. You must specify:</p> <ul> <li>The four numbers a robber is allowed to use to solve your problem</li> <li>and the operations they are allowed to use (note that it's implied by default an answer should use a finite number of operations.)</li> </ul> <p>For example, a good cop post may look like:</p> <blockquote> <p>I remember being set this kind of challenge in school, one of them was quite tricky. I'll just give you the same problem our teacher gave us:</p> <p>Make $24$ using $2,2,2$ and $1$ and any of the operations: multiplication, addition, subtraction, unary negation, division, factorial, square rooting, and modulus.</p> <p>I managed to solve it with three of those operations, maybe you can beat me!</p> </blockquote> <hr> <p>Somewhat-important questions raised in comments:</p> <blockquote> <p>For the example, is the goal is to get 24 out of 2, 2, 2, 1 using 3 operations tops? An answer with 4 operations is not valid.</p> </blockquote> <p>Actually, the cop is not allowed to limit the number of operations. However, unless the cop states otherwise, you should assume that the number of operations you use must be finite.</p> https://puzzling.stackexchange.com/q/25326 -1 Robbers - The ultimate compass challenge [closed] ghosts_in_the_code https://puzzling.stackexchange.com/users/4269 2016-01-13T07:56:58Z 2016-01-13T16:38:30Z <p>Please read the <a href="https://puzzling.stackexchange.com/questions/25325/cops-the-ultimate-compass-challenge">Cops post</a> for all details.</p> <p>Points are scored on the basis of how long a challenge remains unsolved before you solve. You may solve any number of challenges. You cannot solve your own challenges. Points scored by robbers and by cops are independent, and you can participate in both posts separately.</p> https://puzzling.stackexchange.com/q/25325 0 Cops - The ultimate compass challenge [closed] ghosts_in_the_code https://puzzling.stackexchange.com/users/4269 2016-01-13T07:52:19Z 2016-01-13T16:08:51Z <p><em>Based on <a href="https://puzzling.stackexchange.com/questions/24948/the-square-and-the-compass">The square and the compass</a></em></p> <p><em>This is a new kind of challenge proposed on <a href="http://meta.puzzling.stackexchange.com/questions/4508/cops-and-robbers-anyone">Meta Puzzling SE</a>. Any discussion about the general type of puzzle (rather than this particular one) can be done there.</em></p> <p><em>The robbers' post is given <a href="https://puzzling.stackexchange.com/questions/25326/robbers-the-ultimate-compass-challenge">here</a>.</em></p> <p>You have a compass and a pencil but no scale/straightedge. You need to decide upon a construction task that can be achieved accurately in a finite number of moves. The following moves are valid.</p> <ul> <li>Make the compass radius equal to the distance between two already marked points.</li> <li>Draw a circle with any marked point as centre.</li> <li>Use any intersection of arcs/circles as a marked point.</li> <li>Select a continuous region (either an arc or a 2D region) and mark an approximate point. For example, I could draw an arc and then mark a point that is approximately (but not exactly) at the centre.</li> </ul> <p>For example, a task could be "find the midpoint of a line segment" or "mark 5 points that form a regular pentagon"</p> <p>Your challenge will be scored by the amount of time it remains unsolved. At the end of this month (31 Jan), you must post the solution(s) to any unsolved challenges. You can make up to 3 posts, and your total score will be the sum of the individual scores.</p>