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#Post#: 22174--------------------------------------------------
Recreational math
By: Clay Death Date: May 2, 2015, 10:58 pm
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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
#Post#: 27901--------------------------------------------------
Re: Recreational math
By: JFoshia Date: August 27, 2015, 10:51 am
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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
#Post#: 27902--------------------------------------------------
Re: Recreational math
By: JFoshia Date: August 27, 2015, 10:56 am
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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.
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