Hiya all,
I was just thinking about how the books go on and on about teaching our kids that if we
==double the side of a square, the area is quadrupled==
I realized that no one ever says “double the diameter of a circle, ….” so plan 1 is to see if I can create a visualization with geogebra about this. (Anybody got one already?) I presume 8 wedges will be double in height and double in length… http://www.geogebratube.org/student/m111
Magic of 14.
I also realized that nobody ever says the much more useful:
“What number times the side/diameter gives double the area?”
I presume this is because “officially” you need sqrt(2). But 1.4^2=1.96 or almost 2.
Suppose a 10” pizza costs $10 and a 14” pizza costs $18. Should you but two 10” pizzas or one 14” pizza?
(While I was in this problem – I thought to myself: Maybe you get more/less crust … Do you?)
Of course, I only “know” the times tables up to 12. What a pity. 14 is the magic number that gets you (almost) double the area. So if we knew the 14 times table:
· We could check when an 8”pizza was doubled in size. (Answer: 11.2”)
· Or when an image will be half the filesize: (1.4/2=70%) (This is why engineers say: sin(45 degrees)=0.7 or 0.707)
Conclusion: I think the number 14 deserves a lot more of our time :)
Warm regards to all, Linda
Hiya all,
I was just thinking about how the books go on and on about teaching our kids that if we
==double the side of a square, the area is quadrupled==
I realized that no one ever says “double the diameter of a circle, ….” so plan 1 is to see if I can create a visualization with geogebra about this. (Anybody got one already?) I presume 8 wedges will be double in height and double in length… http://www.geogebratube.org/student/m111
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Thanks Alex. I knew you would have applets and information :). As always I appreciate your reply! Thank-you Maria too!
I did manage to make the an easy applet to show double the radius, quadruple the area: http://www.geogebratube.org/student/m29088
I could not for the life of me (or at least 5 hours of me) figure out how to map the ring that sticks out from a 14” pizza into a 10” pizza (since they have the same area). It was interesting to realize that two “opposing” irrational numbers are at play: pi and sqrt(2).
Best, Linda
P.S. This was cool to see in Alex’s pizza applet (The blue is half the red.):
Magic of 14.I also realized that nobody ever says the much more useful:
“What number times the side/diameter gives double the area?”
I presume this is because “officially” you need sqrt(2). But 1.4^2=1.96 or almost 2.
Of course, I only “know” the times tables up to 12. What a pity. 14 is the magic number that gets you (almost) double the area.
Conclusion: I think the number 14 deserves a lot more of our time :)
Hiya!
I think I can do the sweep thing! Thanks so much Alex and Jason for the links. I will report back when I have a working applet.
Thanks Juan - that was fun to read.
Thanks to MathHombre for the tweet (and I was just adding your latest blog to my livebinder when it came in)!
>> how to map the ring that sticks out from a 14” pizza into a 10” pizza
>> (since they have the same area). It was interesting to realize that two “opposing”
>> irrational numbers are at play: pi and sqrt(2).****
>>
>> ** **
>>
>> Best, Linda****
>>
>> P.S. This was cool to see in Alex’s pizza applet (The blue is half
>> I realized that no one ever says “double the diameter of a circle,
>> ….” so plan 1 is to see if I can create a visualization with geogebra about this.
>> (Anybody got one already?) I presume 8 wedges will be double in
>> height and double in length…
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Thank-you Alex for writing this. Good to know it won’t work before I work on it :). I did like the onion peel and I am glad you wrote it up and showed the fourths. Good reference. How you all keep up the energy for blogs – oh my.
Warm regards, Linda