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  Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

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#41951 Re: Help Me ! » equations, equations... » 2005-07-22 16:55:44

GurraTedden wrote:

(three unknown x,y,z with three equations, always solvable right!? But i only want to solve this for x!!!)

There are actually six variables...x,y,z,a,b,c roll

#41952 Re: Help Me ! » Square root of 0 » 2005-07-22 16:46:51

Hi Helen,
I don't know what you mean by pie questions and pie formula.
If you mean pi, I shall explain to you.
Pi is a Greek alphabet used to represent the ratio of the circumference of a circle to its diameter, which is always a constant.
Pi is taken as 3.14 or 22/7, as an approximation,
but the actual value of pi is
3.14159265358979323846264338327950288.......it goes on and on.
The area of a circle of radius 'r' is
pi*r²  and its circumference is 2*pi*r
Similarly, the volume of a sphere of radius'r' is
4/3*pi*r³  and its area is 4*pi*r² .
Pi is also an angle of 180 degrees.
Therefore, pi/2 would be 90 degrees and pi/4 45 degrees.
If you have any specific doubt, you can post in this forum. smile

#41954 Re: Guestbook » maths » 2005-07-21 23:33:10

EveryoneTookTheGoodNames wrote:

Yup - maths is fun, expecially on this website

Great! That's a big compliment, Thank you smile

#41955 Re: Help Me ! » Square root of 0 » 2005-07-21 23:28:10

mathsyperson wrote:

e^(i*pi)=1

Of the five numbers considered important in mathematics, this number relates four.
I think this equation was given by Loenard Euler.
This, I think,  is a result of
e^(i*theta) = cos (theta) + i sin(theta)
and
Abraham de Moivre's theorem, according to which
(Cos(theta)+i*sin(theta))^n = cos n(theta) + i*sin n(theta)
which can be written as
e^(n*i*theta) = Cos n(theta) + i*sin n(theta) roll

#41956 Re: Jai Ganesh's Puzzles » Problems and Solutions » 2005-07-21 22:07:33

Thank you, Admin, for the neat graph. smile

#41957 Re: Jai Ganesh's Puzzles » Problems and Solutions » 2005-07-21 20:52:37

Cos(Sin A) is always greater than Sin (Cos A),
as rightly pointed out by Mathsy!
We shall test this for three values in the first quadrant, in degrees.
First, 0.01°.
Cos (Sin A) > Sin(CosA).
Next, for 45°
Again, Cos (Sin A) > Sin(CosA).
Finally, for 89.9°
Yet again, we get the same result.
I shall try to search for a proof, or prove it myself!

#41960 Re: Jai Ganesh's Puzzles » Problems and Solutions » 2005-07-21 16:35:07

Which is greater?
Cos (Sin A) or Sin (Cos A)?

#41961 Re: Jokes » grand jokes » 2005-07-21 16:33:40

....and I heard the refrigerator was a washing machine! tongue

#41962 Re: Help Me ! » Square root of 0 » 2005-07-21 16:23:52

Hi, I love pi! Welcome to the forum!
Trying to find the square root of 0 using logarithms is not possible
as log 0 is not defnined. This is because any number raised to any number cannot be 0. That includes 0.
The square root, cube root, fourth root etc, of 0 IS 0.
This is because
0² = 0
0³ = 0
0^4 = 0 and so on.
Any nth root of 0 is 0, the only condition being n ≠ 0.
This follows from the fact that
if a^b = c, then bth root of c = a.
The birth of imaginary numbers is, indeed, interesting.
I had read somewhere that imaginary numbers have practical applications too!

#41963 Re: Help Me ! » Difficult question » 2005-07-20 21:21:03

There's a better one! Truly universally acceptable, but not being put into use anywhere (I think! wink )
1,0000 = Myriad
1,0000,0000 = Myllion
1,0000,0000,0000 = Byllion etc.

#41964 Re: Help Me ! » Algebra problem » 2005-07-20 21:17:54

mathsyperson wrote:

My favourite is the one with the square made up of a slightly smaller square and 4 right-angled triangles.

And thats the only one I remember! tongue

#41965 Re: Puzzles and Games » The bad coin » 2005-07-20 19:40:33

1/2
Because there's nothing special about Bill's coin!
Because the probability of getting (head, head and head),
(head, tail, and head) are the same, that is 1/8 !

#41966 Re: This is Cool » Do you think you can? » 2005-07-20 19:32:24

I would be wasting close to 33 years of my life if i did (the American Billion), assuming I don't sleep!

#41967 Re: Jai Ganesh's Puzzles » Problems and Solutions » 2005-07-20 19:27:16

mathsyperson wrote:

Wow, four simultaneous equations...

There are only two:-
9x - 4y = 2,000
7x - 3y = 2,000

Solving for 'x', the annual income of the two can be calculated. They would be 9x and 7x. smile

#41968 Re: Help Me ! » Hi » 2005-07-19 22:22:44

There are two types of decimals:- Terminating and recurring.
A number like 12.5 or 1.25 or 3.75 is a terminating decimal.
On the other hand, sometimes, you have numbers like 0.33333333333333.................,
0.166666666666.....................,
1.6666666666666 etc which are called recurring decimals.
For example, 1'/2 or 1/8 is a terminating decimal.
1/3, 5/6 etc are recurring decimals.
I was talking about how recurring decimals are convereted into rational numbers (that is, fractions).
If that is clear, look at the following illustration.
How do we convert 2.166666666666.............. into a rational number?
Let x = 2.16666666666666666............
10 x = 21.66666666666666666..........  ----------(I)
100x = 216.6666666666666666.........  ----------(II)
Subtracting (I) from (II),
90x = 195,
x = 195/90 or 13/6.
Now, have I made myself clear?

#41969 Re: Jai Ganesh's Puzzles » Problems and Solutions » 2005-07-19 21:58:49

#7
The ratio of annual incomes of two persons is 9:7 and the ratio of their annual expenditure is 4:3. Each of them saves $2000 yearly. Find their annual incomes.

#41970 Re: Help Me ! » Difficult question » 2005-07-19 21:56:38

As simple as that!
But you would have to remember
(1) A second is a billion (US) nanoseconds but not a billion (UK) nanoseconds.
and
(2) An American Gallon is different from a gallon in UK

#41971 Re: Jai Ganesh's Puzzles » Problems and Solutions » 2005-07-19 19:25:30

31,100 = S - [500+0.04(s-10,000)]
31,100 = S -[500 + 0.04s - 400]
31,100 = S - 100 - 0.04s
31,200 = 0.96 S
S = 31,200 / 0.96
S = 32,500 smile

#41972 Re: Jokes » Limericks » 2005-07-19 19:14:54

There once was a person called Mathsy...

#41973 Re: Jai Ganesh's Puzzles » Problems and Solutions » 2005-07-19 16:51:33

Problem #6

A salesman's commission is 5% on all sales up to $10,000 and 4% on all sales exceeding this. He remits $31,100 to his parent company after deducting his commission. His sales was worth $_________.

#41974 Puzzles and Games » The truel » 2005-07-19 16:16:11

Jai Ganesh
Replies: 8

Mr. Black, Mr. Gray, and Mr. White are fighting in a truel. They each get a gun and take turns shooting at each other until only one person is left. Mr. Black, who hits his shot 1/3 of the time, gets to shoot first. Mr. Gray, who hits his shot 2/3 of the time, gets to shoot next, assuming he is still alive. Mr. White, who hits his shot all the time, shoots next, assuming he is also alive. The cycle repeats. If you are Mr. Black, where should you shoot first for the highest chance of survival? roll

#41975 Re: Maths Is Fun - Suggestions and Comments » Math Is Fun » 2005-07-18 22:00:17

Reminded me of an old joke:-

The European Union commissioners have announced that agreement has been reached to adopt English as the preferred language for European communications, rather than German, which was the other possibility.

As part of the negotiations, Her Majesty's Government conceded that English spelling had some room for improvement and has accepted a five-year phased plan for what will be known as EuroEnglish (Euro for short).

In the first year, 's' will be used instead of the soft 'c'. Sertainly, sivil servants will resieve this news with joy. Also, the hard 'c' will be replaced with 'k.' Not only will this klear up konfusion, but typewriters kan have one less letter.

There will be growing publik enthusiasm in the sekond year, when the troublesome 'ph' will be replaced by 'f'. This will make words like 'fotograf' 20 per sent shorter.

In the third year, publik akseptanse of the new spelling kan be expekted to reach the stage where more komplikated changes are possible. Governments will enkourage the removal of double letters, which have always ben a deterent to akurate speling. Also, al wil agre that the horible mes of silent 'e's in the languag is disgrasful, and they would go.

By the fourth year, peopl wil be reseptiv to steps such as replasing 'th' by 'z' and 'w' by 'v'.

During ze fifz year, ze unesesary 'o' kan be dropd from vords kontaining 'ou', and similar changes vud of kors; be aplid to ozer kombinations of leters.

After zis fifz yer, ve vil hav a reli sensibl riten styl. Zer vil b no mor trubls or difikultis and evrivun vil find it ezi tu understand ech ozer. Ze drem vil finali kum tru. smile

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