Math game

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resir014
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Math game

Post by resir014 »

Time for another forum game. Rules are the same as the other silly games, only this time it's about hard math questions. You can also show how each question are solved if you could.

Let's start off with an easy one. Convert the following to its simplest form:

sqrt((x-y)(x+y)+y2)

Good luck :bg:
Last edited by resir014 on Sat Nov 06, 2010 1:17 pm, edited 1 time in total.
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AleksiNir
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Re: Math game

Post by AleksiNir »

Nice idea :D

((x-y)(x+y)+y2)0.5 = x0.5+y
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resir014
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Re: Math game

Post by resir014 »

AleksiNir wrote:Nice idea :D

((x-y)(x+y)+y2)0.5 = x0.5+y
Wrong.

Updated the question for a little hint.
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Mr.J
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Re: Math game

Post by Mr.J »

sqrt((x-y)(x+y)+y2)

√(x²-y²+y²)

√(x²) :scratch:
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Quklis
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Re: Math game

Post by Quklis »

Everything's gonna be fine.. until someone wants to divide by zero.
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AleksiNir
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Re: Math game

Post by AleksiNir »

What about...

sqrt((x-y)(x+y)+y2)

√(x²+y²)
Last edited by AleksiNir on Sat Nov 06, 2010 1:52 pm, edited 2 times in total.
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Herbal
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Re: Math game

Post by Herbal »

√((x-y)(x+y)+y²)=√(x²-xy+xy-y²+y²)=√x²=|x|
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Trigger Happy
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Re: Math game

Post by Trigger Happy »

Guys, you depress me. :( When I see what all I forgot in past 5-7 years from leaving high school. :weep:

Otherwise I think, that match exercises have often more than one transcription of same solution, so this maybe isn't best thing for a game (it can cause confusions and misunderstandings).

I would say Mr.J and Herbal are both right, btw. :hide:
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Re: Math game

Post by FogoRJ »

:iagree: LOL ... I'm scared. :scared: It's been many years... :roll:
Now, just know that I know nothing... :oops:
but, this little game is cool. :bg:
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resir014
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Re: Math game

Post by resir014 »

Mr.J wrote:sqrt((x-y)(x+y)+y2)

√(x²-y²+y²)

√(x²) :scratch:
What I was looking for is "x", but that is acceptable for now.

Your turn. :bg:
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Mr.J
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Re: Math game

Post by Mr.J »

Text question.

Resi wants to know how high a church is. So he measure that the angle of the sun and the ground is 20°. Then he measures that the church's shadow is 195m. How high is the hurch? :scratch:
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AleksiNir
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Re: Math game

Post by AleksiNir »

This time I can't be wrong. :D

I made the answer in paint :P
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Last edited by AleksiNir on Sat Nov 06, 2010 3:30 pm, edited 1 time in total.
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Herbal
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Re: Math game

Post by Herbal »

Almost. You had to use tangens

tg 20°=x/195 m => x=tg 20°*195 m=70,97 m

tg 20°=0,3639
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AleksiNir
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Re: Math game

Post by AleksiNir »

Herbal wrote:Almost. You had to use tangens
:doh: :doh: :doh:
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Re: Math game

Post by Mr.J »

Yes Herbal. :bsmile:

Cosine is adjacent/hypotenuse
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Re: Math game

Post by Trigger Happy »

Guys, if you want help with your homeworks, you can say it directly, not mask it behind a game. otherwise I guessed well, that Herbal will be fast.
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Re: Math game

Post by Herbal »

OK, this will be a bit harder, but not that much.

We have on a Descartes-coordinate system (the usual x,y,z ;)) 3 points, A, B, and C.
A(5,13,1)
B(1,1,-5)
C(3,7,-8)

Tell me, what's the area of ABC triangle.

Hint: if needed, use the Car editor to set up points, just divide them by ten to handle them ^^)
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Darjo
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Re: Math game

Post by Darjo »

AB = √(5-1)²+(13-1)²+(1+5)²=√16+144+6=√166
BC = √(1-3)²+(1-7)²+(-5+8)²=√4+36+3=√43
AC = √(5-3)²+(13-7)²+(1+8)²=√4+36+81=√121=11

Area = √[(166+43+121)²-2(121²+43²+166²)] * 0,25
√[(330)²-2(14641+1849+27556)] * 0,25
√[108900 - 88092 ] * 0,25
√20808 * 0,25 =~ 144,25 * 0,25 =~ 36,062

:)

Good idea, I hope I didn't do any mistake :)
Last edited by Darjo on Sat Nov 06, 2010 7:50 pm, edited 1 time in total.
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Re: Math game

Post by Sikamies »

My vector cross product calculations give: A = 1/2*|BA x BC| = 12*(10)^(1/2).
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Re: Math game

Post by Herbal »

Darjo wrote:AB = √(5-1)²+(13-1)²+(1+5)²=√16+144+6=√166
BC = √(1-3)²+(1-7)²+(-5+8)²=√4+36+3=√43
AC = √(5-3)²+(13-7)²+(1+8)²=√4+36+81=√121=11
;)
Sikamies wrote:My vector cross product calculations give: A = 1/2*|BA x BC| = 12*(10)^(1/2).
=which equals to ~37,9473, which is true! Go ahead, Sikamies! :bg:
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Re: Math game

Post by Sikamies »

Ok, next problem from probabilty theory:

Alfa and Bravo have a meeting at 6 pm.
Alfa arrives at random time between 6.00 pm and 6.20 pm (uniform probability distribution) and goes home after waiting 15 minutes if he has not seen Bravo.
Bravo, similarly, arrives at random time between 6.00 pm and 6.30 pm and goes home after waiting 10 minutes if he has not seen Alfa.
What is the probability that they meet?
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Re: Math game

Post by bduddy »

Argh, this is what I go on the Internet to get away from!

72.9%?
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Re: Math game

Post by Alonsomania »

50%, they do meet or they don't
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Re: Math game

Post by Sikamies »

bduddy wrote:72.9%?
That's correct :clap:
( = 35/48 = ~0.729 )

Your turn :bg:
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Re: Math game

Post by Darjo »

May I ask how you obtained that value :)?
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