| Forum Home | ||||
| PC World Chat | ||||
| Thread ID: 57185 | 2005-04-25 22:29:00 | Weekly maths question | Renmoo (66) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 348834 | 2005-04-29 04:31:00 | How about 1/pi? | Graham L (2) | ||
| 348835 | 2005-04-29 04:44:00 | Because of extreme brilliant brain by all people, I decided to reveal the answer earlier, A = 3, C = 7. Next: Simplify the following equation: (x-a)*(x-b)*(x-c)*(x-d).........(x-z) = ? Note: * means multiply Cheers :)Simplifed with the answer: 2 if x=24 or if x=49 then 8 |
Rob99 (151) | ||
| 348836 | 2005-04-29 05:58:00 | For discrete cuts on the rod the answer is 25%. I worked it out by assuming you hold the rod on the left hand side and make a cut, and you then make the 2nd cut on the piece you are still holding. As the first cut approaches the middle of the rod (from the right hand side, assuming the longer piece is on the left hand side, e.g. cut at the 51st percentile), you have a greater probability that your 2nd cut will provide 3 pieces that can form a triangle. But as your first cut approaches the far end of the rod (per my example, the very right hand side, e.g. cut the rod at the 99th percentile), then you have a lesser probability of completing the triangle with your 2nd cut. I worked it out with a combination of graphs and experimental discrete formulae. But the cuts will not be discrete and I have no idea how to work out the area of an ellipse for non-discrete cuts without cheating. I tried to do a rough representation of a graph but the formatting would not allow it. The graph showed a 0% probability for the 0-50th percentiles of the length of the rod, immediately jumping to close to 100% just after the 50th percentile with a straight line angling down to 0% probability at the 100th percentile on the rod. The area bound by the graph was half of half of the total area = pretty close to 25%. So I was way off with my first guess - out by a factor of 50% perhaps? |
andrew93 (249) | ||
| 348837 | 2005-04-29 08:22:00 | Brilliant Andrew - 25% is correct. | Dally (6292) | ||
| 348838 | 2005-04-29 08:44:00 | Darn it! I thought it was 25% but didn't want to post that in case I was wrong and made an idiot of myself. :p :D | FoxyMX (5) | ||
| 348839 | 2005-04-29 11:40:00 | Foxy, people who have a go whether they are right or wrong are never idiots in my book. To quote Rudyard Kipling:- "If you can meet with triumph and disaster and treat these two imposters both the same" | Dally (6292) | ||
| 348840 | 2005-04-29 12:11:00 | Darn it! I thought it was 25% but didn't want to post that in case I was wrong and made an idiot of myself. :p :D Chicken!!!! :D |
Renmoo (66) | ||
| 348841 | 2005-04-29 23:37:00 | Intuitively you'd think the probability was a lot higher than 25%. If the breaks were performed by people, instead of being random, then it is probable the rod would either be broken into three similar sized pieces, or roughly snapped in half then half again. In which case the probability of making a triangle would approach 100%. Although, if the first break was exactly half way along the rod then you have absolutely no chance of making a triangle. An interesting problem ..... got any more? | andrew93 (249) | ||
| 348842 | 2005-04-30 03:01:00 | Surely a triangle can have one side with length=0. The sum of the angles (180+0+0) still equals 180 (on a plane). ;) | Graham L (2) | ||
| 348843 | 2005-04-30 03:15:00 | There's a name for a triangle with one side of zero lenghth. It is called a "straight line" | Dally (6292) | ||
| 1 2 3 4 5 | |||||