The DW Math Thread

SweetieBot - Lothranis · March 2013

Bezdna - Dreamweaver wrote: »

SweetieBot give 1 point to Decus - Dreamweaver for making this thread.

Aww sorry but you need to have at least 50 posts to be able to award points.

Bezdna - Dreamweaver · March 2013

Noooo, my plan is foiled!

Decus - Dreamweaver · March 2013

Nice try Hex

Think I might go back to 5th grade math for a bit to make this thread more lively again.

Veneir - Dreamweaver · March 2013

Decus - Dreamweaver wrote: »

Nice try Hex

Think I might go back to 5th grade math for a bit to make this thread more lively again.

Like if you take the difference of 300 jumping cats and 168 sitting cats how many standing cats would you have?
....wait what..?

darknessofmy · March 2013

SweetieBot, coutdown to 10

SweetieBot - Lothranis · March 2013

darknessofmy wrote: »

SweetieBot, coutdown to 10

1.(5char)

Decus - Dreamweaver · April 2013

No one wants to do math anymore. Where are Fizban, Cheze, and Yorkin?

More 5th year grade math:

1. If Wacfy were to color in this shape, what are the minimum number of colors required so that no two adjacent shapes have the same color in his drawing? (Please provide an image because waffles.)

2. Veneir is reading a book and the two open page numbers add up to 5895. (It's a big book.) What are the two open pages?

3. Thrivelia decides to go shopping! She sees that bananas are $2 Canadian per pound (because they somehow use pounds in Canada). She wants to buy 4 pounds of bananas, but, for some reason, wants to know how much she'd pay for the banana peels in euros? Thrivelia also remembered a random fact: the weight of a banana is 30% peel. OTL

Veneir - Dreamweaver · April 2013

Veneir does not understand why problem one is a maths problem x3 Also, three.

Nariin - Dreamweaver · April 2013

2. 5895 / 2 = 2947.5 so pages are 2947 and 2948. Wonder how long it took...

Decus - Dreamweaver · April 2013

Nariin - Dreamweaver wrote: »

2. 5895 / 2 = 2947.5 so pages are 2947 and 2948. Wonder how long it took...

I said it was a big book

<

Veneir - Dreamweaver · April 2013

Nariin - Dreamweaver wrote: »

2. 5895 / 2 = 2947.5 so pages are 2947 and 2948. Wonder how long it took...

Probabily a few days. x3

Nariin - Dreamweaver · April 2013

Decus - Dreamweaver wrote: »

I said it was a big book <

Veneir - Dreamweaver wrote: »

Probabily a few days. x3

.-.
.

Q____Q - Dreamweaver · April 2013

Veneir - Dreamweaver wrote: »

Veneir does not understand why problem one is a maths problem x3 Also, three.

I'M SORRY BUT i HAD TO FIX YOUR PICTURE

link!

Veneir - Dreamweaver · April 2013

Q____Q - Dreamweaver wrote: »

I'M SORRY BUT i HAD TO FIX YOUR PICTURE

link!

...Thrivvy
Thrivvy I can bareily tell those are different hues and it does not make looking at that cirlcle at all pleasant--
What are you doing--

Awww, Nari x3

opkossy · April 2013

Decus - Dreamweaver wrote: »

I posted more 5th grade math and you didn't partake

!!!

First Thriv strips the bananas like a twisted sick person. After which, (checking the conversion of Canadian dollars to Euros at 0.75 Euros per dollar) Thriv goes to the local bank and converts 8 dollars to 6 Euros.

... Wait did I solve a problem instead of giving out vague hints? Darn it!

Runemine - Dreamweaver · April 2013

http://www.math.ucla.edu/~yanovsky/handbooks/linear_algebra.pdf Page 35 Problem #7. I dare you to solve it lol.

Decus - Dreamweaver · April 2013

OPKossy wrote: »

!!!

First Thriv strips the bananas like a twisted sick person. After which, (checking the conversion of Canadian dollars to Euros at 0.75 Euros per dollar) Thriv goes to the local bank and converts 8 dollars to 6 Euros.

... Wait did I solve a problem instead of giving out vague hints? Darn it!

~_~;;

Runemine - Dreamweaver wrote: »

http://www.math.ucla.edu/~yanovsky/handbooks/linear_algebra.pdf Page 35 Problem #7. I dare you to solve it lol.

While I did take linear algebra and have an elementary basis in it, I can't solve that. Is that homework for you? 'Coz I can find someone that can solve it if you genuinely need help. If you're just trying to stump me, then you win? Also, I hate proofs.

Runemine - Dreamweaver · April 2013

Lol just trying to stump you. I can understand some of it but yeah rest is gibberish to me.

DuckTapez - Archosaur · April 2013

Decus - Dreamweaver wrote: »

3. Thrivelia decides to go shopping! She sees that bananas are $2 Canadian per pound (because they somehow use pounds in Canada)

I just came here to say that we do, in fact, buy bananas by the pound in Canada b:surrender
(Also, those are some pretty darn expensive bananas)

Decus - Dreamweaver · April 2013

DuckTapez - Archosaur wrote: »

I just came here to say that we do, in fact, buy bananas by the pound in Canada b:surrender
(Also, those are some pretty darn expensive bananas)

Weird, kinda like they use miles in the UK. Yea they were but I just randomly put in numbers, which reminds me...

More problems! Yay! These are not very difficult, and I tried to make them a bit more fun and accessible than the usual. The problems of this thread got really complicated, really fast, and I'd like to bring it back to a more fun and less intense level.

1) If Nariin were to take a modern map of continental South America, what is the minimum number of colors she would have to use to color the countries of the map so that no two adjacent countries have the same color? (To be clear, sharing a point is not the same thing as being adjacent.)

2) Synta is quite perplexed by the fact that the mathematics book he is reading says that 0.999... = 1 and does not elaborate on this seemingly impossible idea! Can you explain this for him in a simple way so he can understand? (That is, give me a short, sweet, and simple proof for it. I know I said I hate proofs, but this one can be quite creative if you give it a bit of time. I want to see the most creative way to reproduce this one.)

3) Runemine was fretting over his Linear Algebra textbook and saw three column vectors that were claimed to be linearly dependent. He is certain that they aren't and the book is wrong! Who is right here, Runemine or the textbook? (Show work! Congrats on inspiring a problem, Rune.)

Fissile - Archosaur · April 2013

Decus - Dreamweaver wrote: »

Evaluate this purty integral.

2*Pi( cos(a) + cos(3a) ) f:confused

Fissile - Archosaur · April 2013

Decus - Dreamweaver wrote: »

3) Runemine was fretting over his Linear Algebra textbook and saw three column vectors that were claimed to be linearly dependent. He is certain that they aren't and the book is wrong! Who is right here, Runemine or the textbook? (Show work! Congrats on inspiring a problem, Rune.)

If you call the three vectors u, v, and w then w = 1.5u - 0.5v so they are not linearly independent.

Decus - Dreamweaver · April 2013

Fissile - Archosaur wrote: »

2*Pi( cos(a) + cos(3a) ) f:confused

Hmm, no, that's not right. I need to double check though. I appreciate you doing an old problem

Fissile - Archosaur wrote: »

If you call the three vectors u, v, and w then w = 1.5u - 0.5v so they are not linearly independent.

Yep, correctomundo! (Try to leave the other two now for other participants.) Thanks for contributing to my little thread!

Q____Q - Dreamweaver · April 2013

Decus - Dreamweaver wrote: »

1) If Nariin were to take a modern map of continental South America, what is the minimum number of colors she would have to use to color the countries of the map so that no two adjacent countries have the same color? (To be clear, sharing a point is not the same thing as being adjacent.)

a lot? you should've gave me a map =[
is this a map? http://www.ducksters.com/geography/south_america_map_coloring.jpg

EDIT:! oh I THINK THE ANSWER IS 4! IDK :D here's my map: http://i.imgur.com/vn0kgJ3.png
ps i didn't know that south america had like 10 countries

Decus - Dreamweaver wrote: »

2) Synta is quite perplexed by the fact that the mathematics book he is reading says that 0.999... = 1 and does not elaborate on this seemingly impossible idea! Can you explain this for him in a simple way so he can understand? (That is, give me a short, sweet, and simple proof for it. I know I said I hate proofs, but this one can be quite creative if you give it a bit of time. I want to see the most creative way to reproduce this one.)

it's like that thread on dyna forums with the math clock... and how the 7 on clock was 6.9 and the nine had the line thingy on it.... OTL he will never understand!

Fissile - Archosaur · April 2013

f:gone

Consider the series N where:
N[1] = 0.9 = 1 - 0.1
N[2] = 0.99 = 1 - 0.01
N[3] = 0.999 = 1 - 0.001
...
N = 1 - 0.1 ^ i

Then Lim( N, i -> infinity ) = 0.99999999... = 1 - Lim( 1 / (10 ^ i), i -> infinity ) = 1 - 0 = 1

Fissile - Archosaur · April 2013

Decus - Dreamweaver wrote: »

Hmm, no, that's not right. I need to double check though. I appreciate you doing an old problem

Pretty sure the integrand can be rewritten as:

2(cos(a)+cos(3a)+cos(x)+cos(3x)+cos(a-2x)+cos(2a-x)+cos(2a+x)+cos(a+2x))

The antiderivative is:

2x (cos(a)+cos(3a)) + (some junk)

Where every term in (some junk) is multiplied by a sin(n*x) term, which all evaluate to 0 at each of the limits of integration. So evaluating at the limits:

2*Pi*(cos(a)+cos(3a)) - 2*0*(cos(a)+cos(3a)) + (some junk that evaluates to 0)

Decus - Dreamweaver · April 2013

Fissile - Archosaur wrote: »

f:gone

Consider the series N where:
N[1] = 0.9 = 1 - 0.1
N[2] = 0.99 = 1 - 0.01
N[3] = 0.999 = 1 - 0.001
...
N = 1 - 0.1 ^ i

Then Lim( N, i -> infinity ) = 0.99999999... = 1 - Lim( 1 / (10 ^ i), i -> infinity ) = 1 - 0 = 1

Yep, this will suffice, though I did ask you to let someone else give the other problems a shot =p

I still want more submissions for this one anyway since I'd like to see how other people approach it.

Fissile - Archosaur wrote: »

2*Pi*(cos(a)+cos(3a)) - 2*0*(cos(a)+cos(3a)) + (some junk that evaluates to 0)

Hah, you're totally right! I'm dumb because I somehow managed to ignore the limits of integration in the problem I assigned and thus I couldn't see where Pi played a role and assumed you used an identity of which I wasn't aware. Bravo!

Arctix - Dreamweaver · April 2013

Decus - Dreamweaver wrote: »

Yep, this will suffice, though I did ask you to let someone else give the other problems a shot =p

I still want more submissions for this one anyway since I'd like to see how other people approach it.

I'll try it in the dyna way

Wacky wants to kiss decus, but decus is 1km (1000 m) away.So wacky uses holy path and runs to him. As wacky covers more n more distance she comes nearer to decii. As he has covered 999m he has only 1m to cover so he leans over to kiss. The distance keeps shrinking between them from 1m to 1 cm to 1mm to 1nm to 1A* so as the distance between them decreases more n more they get nearer n nearer considerably. Thus at a particular limit of distance (999.99999999.....m in our case) Wacky finally kisses decus

b:shocked Scary

Veneir - Dreamweaver · April 2013

Arctix - Dreamweaver wrote: »

I'll try it in the dyna way

Wacky wants to kiss decus, but decus is 1km (1000 m) away.So wacky uses holy path and runs to him. As wacky covers more n more distance she comes nearer to decii. As he has covered 999m he has only 1m to cover so he leans over to kiss. The distance keeps shrinking between them from 1m to 1 cm to 1mm to 1nm to 1A* so as the distance between them decreases more n more they get nearer n nearer considerably. Thus at a particular limit of distance (999.99999999.....m in our case) Wacky finally kisses decus

b:shocked Scary

Pfffff x33333 *facedesks*

My doing that problem was boring, I just went by the standard rounding rule that they teach in like third grade or something and disappointed the creative aspect 3:

Synta - Dreamweaver · April 2013

Decus - Dreamweaver wrote: »

2) Synta is quite perplexed by the fact that the mathematics book he is reading says that 0.999... = 1 and does not elaborate on this seemingly impossible idea! Can you explain this for him in a simple way so he can understand? (That is, give me a short, sweet, and simple proof for it. I know I said I hate proofs, but this one can be quite creative if you give it a bit of time. I want to see the most creative way to reproduce this one.)

Uh, hmm

I like this proof, but it's a bit circular /O\

The DW Math Thread

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