The Maths and Science Thread - Collection of Problems and Facts

[TumTum]

Ok, I think I got it.. He was 1 mile north of a latitude that was 1 mile in circumference.
He goes 1 mile south, to the latitude, and does 1 mile east, thus, goes around the latitude and reaches the same place. Then goes 1 mile north to the same place where he started.

So he must have started just above the South Pole.

 

[Abhas]

Yes, Just above the south pole.. where 2 x 3.14 x R = 1 Mile

 

[TumTum]

Yes, Just above the south pole.. where 2 x 3.14 x R = 1 Mile

It's impossible to calculate because the earth is a sphere. R will be the radius from the inside and not the outside.

 

[Abhas]

I made a shite image trying to show what I mean to say..
You can tilt the image 23 degrees to make it the actual earth, but the concept would remain the same.

 

[TumTum]

I made a shite image trying to show what I mean to say..
You can tilt the image 23 degrees to make it the actual earth, but the concept would remain the same.

I know what you mean. just saying it's not easy to calculate the latitude.

 

[Abhas]

Yeah I understand your point.. came across this Math Forum - Ask Dr. Math
This is the only way I found that can calculate the exact latitude.

 

[Varun]

Ok, I think I got it.. He was 1 mile north of a latitude that was 1 mile in circumference.
He goes 1 mile south, to the latitude, and does 1 mile east, thus, goes around the latitude and reaches the same place. Then goes 1 mile north to the same place where he started.

You got it. Intelligent work!

 

[Varun]

Good one! Can any great mathematician solve it?


Two mathematicians, A and B, chat. A says he has three children who all have the same birthday (but who weren't necessarily born in the same year). B asks their ages. A replies, "The product of the ages of my children is 72." B points out that this is not enough information to determine their ages. A responds with another clue -- he tells B the sum of the ages of his children. But B again points out that there is not enough information. Finally A says, "My youngest child is named C." At last, B correctly determines the ages of A's children. What are the ages?

 

[Abhas]

he tells B the sum of the ages of his children.

But you aren't telling us. Cheating!

 

[TumTum]

Good one! Can any great mathematician solve it?


Two mathematicians, A and B, chat. A says he has three children who all have the same birthday (but who weren't necessarily born in the same year). B asks their ages. A replies, "The product of the ages of my children is 72." B points out that this is not enough information to determine their ages. A responds with another clue -- he tells B the sum of the ages of his children. But B again points out that there is not enough information. Finally A says, "My youngest child is named C." At last, B correctly determines the ages of A's children. What are the ages?

3,3,8 = 14
3,4,6 = 13
1,6,12 = 19
1,8,9 = 18
1,1,72 = 74
1,3,24 = 28
1,2,36 = 39
1,4,18 = 23
2,3,12 = 17
2,4,9 = 15
2,6,6 = 14

So it is either the 1st or the last one. But as he says "youngest" their ages are 2, 6 and 6.

 

[Varun]

^You're right!! You did it yourself or....?

 

[TumTum]

^You're right!! You did it yourself or....?

Yep. I was first confused like Abhas but I decided to do it. Then I noticed the trick which was to find the combinations with the same addition.

That was a very good question.

 

[blake]

A quick science question, if anybody can help...

I am a bit confused right now regarding metal extraction. How is ionic bonding relevant to metal extraction? Basically we did a short extraction experiment where we had to extract pure copper from a copper ore but I am still a little confused in the lab report, where I am supposed to list how solubility, states of matter and ionic bonding are relevant...

I think that solubility is important because the positive ions attract the negative ions, but I'm still struggling a bit as to how this purifies the copper..

Any help?

 

[Pranav]

In an electrolytic cell external source of voltage is used to bring about
a chemical reaction. The electrochemical processes are of great importance
in the laboratory and the chemical industry. One of the simplest electrolytic
cell consists of two copper strips dipping in an aqueous solution of
copper sulphate. If a DC voltage is applied to the two electrodes, then
Cu 2+ ions discharge at the cathode (negatively charged) and the following
reaction takes place:
Cu2+(aq) + 2e– → Cu (s)
Copper metal is deposited on the cathode. At the anode, copper is
converted into Cu2+ ions by the reaction:
Cu(s) → Cu2+(s) + 2e–
Thus copper is dissolved (oxidised) at anode and deposited
(reduced) at cathode. This is the basis for an industrial process in
which impure copper is converted into copper of high purity. The
impure copper is made an anode that dissolves on passing current
and pure copper is deposited at the cathode. Many metals like Na, Mg,
Al, etc. are produced on large scale by electrochemical reduction of
their respective cations where no suitable chemical reducing agents
are available for this purpose.

It's an extract from my current Chemistry textbook.

I think it should answer your question.

 

[blake]

Thanks heaps Pranav, explains a fair bit. Cheers man.