Member: reinout-g

Melody:
I just stumbled on this you tube clip.
I thought it was quite good. That is because it is basically the way I teach it (I have looked at many methods in the past and i like this one)
My only criticism of this clip is that he keeps waving his pen about and it is a distraction.
http://www.youtube.com/watch?v=ZQ-NRsWhOGI
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I was thinking that we could start a thread, where the url's of the resources that we like, are added.
Maybe they could be posted individually when first introduced but then assigned to a thread bank of resources.
Does this sound like something people would want to do?
Or is it easier just to go find them each time on the web?
Obviously there are a lot of resources out there. Some are good, some are really not.
also, we won't all like the same ones.

I am just looking for some comments/ideas please.
Would anyone, other than me, like to organize something like this. If not, it doesn't matter. I know you are all busy people.
We could even have our own post within the thread that we look after with edits and additions for ourselves. Do you understand what i mean?
Thanks,
Melody.

I think it is a good idea to have a thread where everyone can share his or her recources.
I'd use it to give quicker answers to the similar questions that are asked every day.
People might share recources which are not so useful (could be a man waving a pen through the screen (just kidding )) but we're not obliged to use them in our answers.
Simply watch the recource before your use it in an answer and then it will probably be an excellent idea!
How about this thread?

reinout-gFeb 5, 2014

#68

+2353

Melody:
HARD ONE
2 2 5 7 17 20 and the magic number is 1994

Maybe we could have a little hint ? Please Reinout-g

Hint: 1994/2 = 997

reinout-gFeb 5, 2014

+2353

Melody:
gutierrez:
three cousins, allan,bob,and charlie,were sitting around watching football on tv. the game was really boring, so they started talking about how old they were. allan (the oldest)noticed that they were all between the ages 11 and 30. bob noticed that the sum of their ages was 70. charlie (the youngest) stated, "gee, if you write the square of each of our ages, all the digits from 1 to 9 will appear exactly once in the digits of the three squares. how old was each person?

I did it entirely by myself.
I used excel just for ease of presentation.
There is only one solution for the squares part.
I did not use the total 70 in any calculation.

Charlie is 19, Bob is 23 and Allen is 28

140204 ABC age puzzle.JPG

I am seriously missing a like button here!
* like *

reinout-gFeb 5, 2014

+2353

AngelIshtar7:
Ranges from 6.57 to 7.93. Write the desired point ± tolerance statement. How do I do this?

Hi Angellshtar,

I assume this question is a subquestion of a bigger exercise.
I believe we might be able to answer your question more accurately if you post the rest of the questions along with this question.
Even though you might already know the answer to those it could help us understand your question.

reinout-gFeb 5, 2014

+2353

gutierrez:
three cousins, allan,bob,and charlie,were sitting around watching football on tv. the game was really boring, so they started talking about how old they were. allan (the oldest)noticed that they were all between the ages 11 and 30. bob noticed that the sum of their ages was 70. charlie (the youngest) stated, "gee, if you write the square of each of our ages, all the digits from 1 to 9 will appear exactly once in the digits of the three squares. how old was each person?

D**n, I don't think I will be able to sleep tonight after reading this.
Will think about it and hope to get back to you.

reinout-gFeb 3, 2014

+2353

Melody:
Hi Reinout-g

Thanks for looking into all this for us.
I am quite impressed with what you have found and displayed in this post.

Do you mind giving it a new title
(we can do that in this forum)
Maybe call it something like 'Display tips' or 'Mathematics display ideas' or something like that.
And put the i symbol in the margin title.

I use some display techniques that i probably should share with people too.
This would make a really worth while ongoing thread'

I am not so impressed the log display page. This caclulator does some weird things.

also, how do i display the quadratic formula, i am obviously not doing it correctly.

[input]x=(-b+-sqrt(b^2-4ac))/(2a)[/input]

Thanks.

Hey Melody,

I sent you a pm on most of your questions but did want to answer this one seperately.

The calculator doesn't give you the right output, simply because it can't give you an answer to the equation.

Obviously the calculator is not meant to calculate instead of formulate (even though it might sometimes be useful for that).

the equation x=(-b{+ or -}sqrt(b ²-4ac))/(2a) is not solvable since there is no x on the right side.

reinout-gFeb 3, 2014

+2353

theiswe:
f(x) = 3^((1/3)(x^3 - 3x)) = 0 Df = R (it says that, what does it mean?)

changed it to this:
f(x) = 3^(x^3/3 - x) -1 = 0

Answer:
x1: (0,0)
x2: (sqrt3, 0)
x3: (-sqrt3, 0)

Tried to solve this by hand. Found (0,0) alright, but cant seem to find how X can be +- square root 3..

PLEASE help fast!! ))

It is getting pretty late here, so I'm going to have to go, but I'll bump this up so it will be answered.

reinout-gJan 29, 2014

+2353

Halper:
The legs are both 4. Add 4 + 4 + 4 (root 2). 8 + 4 (root 2) is your answer.

I am sorry halper but I believe that that is not entirely the correct answer.

The two triangles that were formed by the altitude line are also isosceles triangles because the angles are 90, 45 and 45 degrees.

Therefore, we can use pythagoras to calculate

a ² = b ² + c ²

a = sqrt(b ² + c ²)

We use a for the bottom, b = 4sqrt(2) for the altitude line and c = 4sqrt(2) for half of the hypotenuse.

Then the bottom is given by

[input]sqrt((4sqrt(2))^2 + (4sqrt(2))^2))[/input]

We know that the bottom is equal to the left side since it is an isosceles triangle,

The area of a triangle is given by base*height*1/2 which then amounts to 8*8*1/2 = 32

Hence the area of the triangle is 32

reinout-gJan 29, 2014

+2353

Roregel:
a ball rebounds one half the height from which it is dropped. the ball is dropped from a height of 160ft and keeps bouncing. what is the total vertical distance the ball will travel from the momement it is dropped to the momement it hits the floor for the fifth time?

You can approach the problem by computing it seperately for each bounce.

First the ball travels 160 ft

(hit the floor once)

the ball travels up 80 ft and down another 80 ft

So the total distance travelled is 160 + 80 + 80 = 320ft

(hit the floor twice)

the ball travels up 40 ft and down another 40 ft

So the total distance travelled is 160 + 80 + 80 + 40 + 40 = 320 + 40 + 40 = 400ft

(hit the floor three times)

the ball travels up 20 ft and down another 20 ft

So the total distance travelled is 160 + 80 + 80 + 40 + 40 + 20 + 20 = 400 + 20 + 20 = 440ft

(hit the floor four times)

the ball travels up 10 ft and down another 10 ft

So the total distance travelled is 160 + 80 + 80 + 40 + 40 + 20 + 20 + 10 + 10 = 440 + 10 + 10 = 460ft

(hit the floor five times)

Hence, the ball travels 460ft before it hits the floor five times.

reinout-gJan 29, 2014

+2353

And I have already found that it does not agree with me

As an illustration, it can work with irreal numbers;

reinout-gJan 29, 2014

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