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CAMELOT FREE EDUCATION CENTER => MATH COURSES => Topic started by: Clay Death on May 02, 2015, 10:58:24 pm

Title: Re: Recreational math
Post by: JFoshia on August 27, 2015, 10:56:38 am

Squaring 2-Digit Numbers That End In 5

Example:
  35
x35


The answer will end in 25 (because 5x5=25) so write that down.
Then, look at the tens digit (3). Multiply that number by the number that is one greater than it: 4
Write that answer in front of the 25.
So your answer will be 1,225

It works for squaring any 2-digit number that ends in 5.

           

Title: Re: Recreational math
Post by: JFoshia on August 27, 2015, 10:51:12 am

A quick little math trick: A Fibonacci Sequence problem.

Can you add these numbers up in your head?

2
2
4                            Here is the trick: Take the 7th number down (26)
6                            Add the tens digit to the number: 26+2=28
10                          Then you just tack on the ones digit at the end! 286
16                          So, all ten numbers in this sequence to the left will add up to 286 :)
26
42
68
110

Title: Recreational math
Post by: Clay Death on May 02, 2015, 10:58:24 pm

Doodling in Math and more

https://www.khanacademy.org/math/recreational-math/vi-hart




Puzzles

https://www.khanacademy.org/math/recreational-math/puzzles




Math warmups

https://www.khanacademy.org/math/recreational-math/math-warmup