Melody

Hi Mathhemathh,

I am really pleased that you have become a member.  Welcome to our web2.0calc.com  forum.      

This is the sum of a GP over the sum of another GP

Both have a common ratio of a  and both have 7 terms      r=a   and n=7

\(\mbox{The sum of a GP } = \frac{T_1(r^n-1)}{r-1}    \)

\(answer \\ = \left( \frac{a(a^7-1)}{(a-1)} \right ) \div \left(\frac{a^3 (a^7-1)}{(a-1)} \right)\\ = \left( \frac{a(a^7-1)}{(a-1)} \right ) \times \left(\frac{(a-1)}{a^3 (a^7-1)} \right)\\ =\frac{1}{a^2}\)

I didn't know that the site calc was broken!

Or it could be -9 since   -9*-9 = +81 too

@@ What is Happening?  [Wrap4]    Thurs 12/11/15   Sydney, Australia Time 6:22pm   ♪ ♫

A good day to you all,

Our fabulous answers have been provided by Heureka, Alan, CPhill and Saseflower.  A very big thank you to each of you.     

Repeat request:

In the post below where I have invited people to discuss their views of the forum.  All sensible thoughts will be greatly appreciated.

8b^3/7t^2 * 49t^4/64b

The problem here is your lack of brackets.

People are guessing what you may mean.

Technically, (using the rules of PEDMAS) this is your meaning

\(\frac{8b^3}{7}\times t^2 \times \frac{49t^4}{64}\times b\)

Heureka has interpreted what he thinks you meant NOT what you wrote down. We commonly do this.

I am not sure what our guests did.

WOW Chris,

You do have a great wealth of abilities.  I am impressed !

I knew you were a mathematician but now I see you are a poet as well.     

Shaving your face with a garden trowel is a pretty amazing skill that you possess too. :))

According to Wolfram|Alpha, the probability that at least 3 people have the same birthday is 0.06689

In the top 40 rankings of men tennis players, what is the probability that at least 3 of them share the same birthday(the same day of the year?) Your answer must be accurate to 3 decimal places. You must give the method used in your calculation. Good luck to all.

This is what Wolfram|alpha has to say

I also found some formuals here 

http://math.stackexchange.com/questions/25876/probability-of-3-people-in-a-room-of-30-having-the-same-birthday

I have not looked very hard at the formulas but i doubt that their derivation is trivial. 

They may well be valid but to use them without understanding is no better than to just cut and past a page from Wolfram|Alpha.  (Unless you want to use it for computer output or something. Of course Wolfram Alpha has generated its answers from formulas in the first place)

Hi Saseflower,

Thanks  very much for adding your concerns here.  I really appreciate it.    

The point you make in your first post      #5   is extremely important.

We need to be able to find our own posts and other people's post.  It is extremely important for the effective runnig of the forum.     Hopefully we will get this function back again soon. 

Except for the access problems that some people are having it is the BIGGEST concern to us.

-----------------------------------

Your second point  #6

You can still edit your posts :)

Press the little downwards arrow that is to the right of your post number    For example  #6

and you will get a drop down menu.  Edit is one of the choices  

The sum of two intergers is -41. The greater number minus the lesser number is 13. Which is the greater of the two numbers?

let the numbers be x and y,  the big one is x

x+y=-41     (1)

x-y = 13     (2)

find  x

add the 2 equations

x+y     +x-y  =  -41+13

the ys cancel out

2x= -28

x = -14

Check

find y from equ (1)      

-14+y=-41

so y= -41+14 = -27

sub into equation (2)     -14 - - 27 = -14 + 27 = 13    excellent

The biggest number is   -14

Could you help me come up with a math problem involving basic logarithm with an answer of 3567? Thank you! 

\(log_2 2^{3567}=3567\)