Hard Math Question

Sorry guys, but I'm looking for a mathmatition on this one...this has me stumped for hours. Could someone help me with this one??


The length of a rectangle is 5 cm less than twice the width. The perimeter is is 35 cm. What are the dimensions of the rectangle?

:banghead: :banghead: :banghead:
Thanks...lol, good luck.

I get 10 and 10 for length and 7.5 and 7.5 for width.

Been years since I did this but I think this is right..

2(2w-5)+2w=35
4w-10+2w=35
6w=45

w=7.5


now for the length

2w-5

2(7.5)=15

15-5=10

Length is 10 (2 for both sided) = 20
Width is 7.5 (2 for both sides) = 15


= 35


Ok twice width (of 7.5) is 15 - 5 = the 10. length is 5 less then twice the width.

Rob

great, thanks man....it doesnt sound that damn hard when I read you saying it.... thanks again

Dang, beat me to it. I was at school when you posted this. :(

Hey tangy, how about this one.. what is the recursive formula for the sequence 1, 1, 2, 4, 7, 13?

I'm going to need some time to get the recursive formula just right, but I can see the pattern now. Give me a few minutes.

Hey tangy, how about this one.. what is the recursive formula for the sequence 1, 1, 2, 4, 7, 13?

Okay, I defined it as:

F(n) = 1 if n = 0 or 1
..........F(n-1) + F(n-2) if n = 2
..........F(n-1) + F(n-2) + F(n-3) otherwise

Another alternative could be to simply state that F(n) = n if n=2 or F(n) = 2 if n=2. I hope that's what you were looking for.

Basically, this is like a modification on Fibonacci's sequence. However, instead of only adding the last two numbers in the sequence, you add the last 3 (at least from n = 3 and upward).

ok ok, I got one



1+1=?

11 ;) I win.

11 ;) I win.
No way jose...its window



:p




I have too many younger siblings

Okay, I defined it as:

F(n) = 1 if n = 0 or 1
..........F(n-1) + F(n-2) if n = 2
..........F(n-1) + F(n-2) + F(n-3) otherwise

Another alternative could be to simply state that F(n) = n if n=2 or F(n) = 2 if n=2. I hope that's what you were looking for.

Basically, this is like a modification on Fibonacci's sequence. However, instead of only adding the last two numbers in the sequence, you add the last 3 (at least from n = 3 and upward).
That works perfect, thanks

And yeah, its just like the fibonacci sequence

Speaking of Fibonacci, does anyone have any cool ways that I could introduce that pattern to a bunch of 12 year olds? Maybe someone did something really cool with it? I need to teach patterns next week, and I really want to use Fibonacci's sequence, but it needs to be simple... no recursive formulas or higher-order thinking.

Maybe find a bunch of interesting examples of the fibonacci sequence in nature, like sunflowers and whatnot. Kids are intriguied by those kinds of things, finding a secret sequence of mathimatical numbers that have patterns in the world. Its good stuff

pine cones... i think that might be one of the easiest ways, because kids are always doing something with them, like making bird feeders and stuff. but i guess it depends where you live. hopefully you have pine trees

I can easily find Fibonacci in pineapples, pine cones or sunflowers, but these kids are in 7th grade, so I'm not entirely sure if they will still be interested in something like that. I need something to get the kids motivated because I'm being observed by my supervisor, and she wants to see student to student interaction.

Tangie- At no point in my schooling was I ever intrigued by pinecones, or other learning devices. just present the material and they'll pick it up. I've never heard of fibonacci's sequence intil this thread, but I immediately understood it. it's really not a difficult pattern, just start out slow. You're a young female teacher, I guarantee you that you'll at least have all the guy's attentions.

uhm.... E=MC2???

The point isn't to mesmerize them with my "femininity", we shall call it. And I don't JUST want to focus on Fibonacci because it shouldn't take them long to see the pattern, I HOPE (but after this week, who knows what the hell these kids know... it's been bad, we'll just say that). I wanted to come up with SOMETHING that is a bit more interesting than me standing at the overhead lecturing. I took in their class pet for the first time today (a goldfish) and they were all AMAZED by it. Maybe you can at least give me some ideas of other cool patterns you have found (just numbers at this point). I might show them the golden mean after we do Fibonacci, but that might blow them away.