Welcome to CuriousMath.com

Friday, March 14, 2008 - 10:51 AM

Posted by clay

2227 Reads

In honor of Pi Day 2008, I thought I would post a little article about the remarkable, infinite, and irrational Pi.

Wednesday, February 27, 2008 - 01:28 PM

Posted by Farisnet

3015 Reads

As inspired by Gauss's tale of impressive summation of all integers from 1 to 100, I set out to have a formula that would sum all the numbers between two numbers, inclusive.

Thursday, November 16, 2006 - 08:26 PM

Posted by ArunChaganty

15279 Reads

Clay's article was an excellent, and a very well explained one too. I'd just like to add the bit about the probability of the odds of finding a person with the same birthday as you. Hopefully mine will be as descriptive as his.

In this article, we shall explore some techniques of probability, and 'permutations and combinations'. This is going to be a slightly long article, but is very much educative, and I'll try to cover the entire thing from front to back. You can skip bits if you know them, but for the benefit of those who don't I've included them. I've finally posted a way of doing the question without any of this knowledge, but I still think you should read and understand what I'm trying to explain.

Thursday, August 17, 2006 - 11:19 PM

Posted by clay

33425 Reads

Here's a fun and easy application of probability to show the odds are good that two people in a relatively small group will share the same birthday.

Friday, June 02, 2006 - 06:20 AM

Posted by ScottC

55856 Reads

When asked to do division in your head, it's very impressive to be able to carry the answer out to several decimal places. When dividing by a 1-digit number, it's not that difficult, either.

Sunday, March 26, 2006 - 06:46 AM

Posted by puneet478

23354 Reads

This is one of the best methods used to create a magic square of any order. I will start with an example of 3*3 grid to explain the method.

Saturday, March 11, 2006 - 05:59 PM

Posted by ArunChaganty

21006 Reads

Two days before my major exam, my friend and I sat down to play with magic squares. Obviously a big mistake, but I actually did the best of all in that particular exam. I think it came from cracking the code for any odd magic square.

Saturday, March 11, 2006 - 05:16 PM

Posted by ArunChaganty

20089 Reads

This is a rather well known concept (at least where I'm at), but I thought I might as well post it. I proved it yesterday, and so I thought I'd share it with you all.

Sunday, November 27, 2005 - 09:57 AM

Posted by the_desire

29116 Reads

The sum of any cube when reduced to a single digit will always be either 1, 8, or 9.

Monday, July 18, 2005 - 11:44 AM

Posted by j2020j0908

92836 Reads

The trick I am going to explain is called the cross-multiplication technique... but not the one you know.

Sunday, June 26, 2005 - 08:13 AM

Posted by mathmate

60104 Reads

The other day I was strolling in a part of the city where street vendors compete for the tourist dollar. I came across a young lady, felt marker in hand in front of an easel displaying a 6x6 array of numbers. It was a hot day, and it took an effort just to stand among the crowd at the same time understand what she was explaining. Curiosity won over me and here's what I found.

Monday, December 27, 2004 - 06:30 AM

Posted by mathmate

49038 Reads

You probably know that 3² + 4² = 5². Those three whole numbers, known as "Pythagoras Triplets", satisfy the Pythagoras Theorem, a² + b² = c². Did you know there are many more such whole number triplets? This article shows you one method of finding them.

Saturday, December 11, 2004 - 03:04 PM

Posted by mathmate

42805 Reads

You may have heard the recent news of Dr. Gert Mittring, who correctly extracted the 13th root of a 100-digit number in less than 12 seconds...in his head. This article shows you how to accomplish the same feat in the same amount of time using an ordinary calculator.

Wednesday, December 08, 2004 - 07:21 AM

Posted by guil140

53088 Reads

With the help of logarithms, you can do some pretty amazing mental calculations. This article shows you how.

Tuesday, September 07, 2004 - 11:25 AM

Posted by capperdisc63

161226 Reads

No symbols and characters allowed. (Here's a hint: it's not 999)

Monday, August 09, 2004 - 09:33 PM

Posted by flyers2000

42554 Reads

I came up with this method for determing the logarithm (base 10) of a number in my head back in 1995. I was tutoring a friend for her MCAT exams and a question involving pH and pKa values struck my interest. Although we were able to arrive at a suitable answer without actually needing a calculation, I still wanted a quick way of determining logarithms in the event that I found myself without a calculator (and just as a mental challenge for myself).

Thursday, February 26, 2004 - 04:01 PM

Posted by kayer35

52870 Reads

Here's how you can directly write down the answer to any number multiplied by 11.

Thursday, February 26, 2004 - 03:57 PM

Posted by kayer35

82630 Reads

Got 5 minutes to spare? That's all the time you need to learn how to quickly multiply two numbers from 11 to 19 in your head.

Monday, December 15, 2003 - 11:02 AM

Posted by sancle

52552 Reads

Ask anyone to select a number less than 1000, and to divide it respectively by 7, 11, and 13, giving you the three remainders. You will then be able to tell him what number he originally selected.

Tuesday, October 28, 2003 - 03:15 PM

Posted by PiInTheFace314

65738 Reads

Like they said, it’s hip to be square! Here are a few easy tricks that’ll make squaring numbers much faster.

Tuesday, September 30, 2003 - 11:58 AM

Posted by deud

57341 Reads

If you want to add all the numbers from F (First) to L (Last), here is an easy way to do it, and many times can be performed in your head.

Friday, September 12, 2003 - 09:32 AM

Posted by deud

46745 Reads

Sometimes a difficult percentage calculation can be made easy simply by swapping the two terms.

Monday, June 09, 2003 - 10:07 AM

Posted by clay

39698 Reads

The number classification you’re probably most familiar with is odd and even. Even numbers can be divided into two equal parts without a remainder. Odd numbers can’t. End of story, right? Not according to Boethius. He divides even numbers into three types.

Saturday, May 17, 2003 - 09:45 AM

Posted by louisflorian

83614 Reads

Interesting products for various multiplication problems. Not very useful, but certainly curious.

Tuesday, April 22, 2003 - 06:58 AM

Posted by Einstein323

30256 Reads

To multiply any three-digit number that has similar digits (e.g. 333) by eleven, you can apply certain rules. These following rules might be complicated and you might find no use for them, but they're quite interesting.

Friday, March 14, 2003 - 06:08 PM

Posted by clay

91726 Reads

If someone cubed a two-digit number on a calculator and gave you the result - but not the original number - could you extract the cube root? With this trick, you'll be able to do just that - instantly!

Tuesday, February 11, 2003 - 01:52 PM

Posted by clay

64522 Reads

Ever wonder where math words come from or how they developed? I do. That's why I put this section together. I know it's a short list but, heck, you wouldn't read it if it was long.

Tuesday, February 11, 2003 - 01:33 PM

Posted by clay

35636 Reads

Here are a few recipes for spicing up your squaring excitement. They're not necessarily easy or quick, but I think they're worth knowing if you're into math tricks.

Tuesday, February 11, 2003 - 01:04 PM

Posted by clay

82388 Reads

Ever wonder how to determine the square root of a number without the aid of a calculator? Believe it or not, people used to do this. Here's one method for doing so.

Tuesday, February 11, 2003 - 09:06 AM

Posted by clay

90353 Reads

A friend of mine e-mailed this to me a long time ago. Give it try, it's pretty neat. The rules are simple: just scroll down slowly.