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 #4
avatar+118723 
+11

https://m.youtube.com/watch?v=8w_lwezZDUw

This music has got a great beat :)

It has a catchy little tune too :)Thanks for sharing Dbg  

May 20, 2015
 #45
avatar+118723 
0

@@ End of Day Wrap   Wed 20/5/15   Sydney, Australia Time   12:30am  (Thurs really) ♪ ♫

 

Hi all, 

 

Great answers today from:  Alan, CPhill, Andrew1714, TheJamesMachine, Dbg4thebest, MathsGod1, DarkBlaze347, ShadowBolt04, Zacismyname, Heureka, GoldenLeaf, MathWitch and Badinage.  Thank you. 

 

If you would like to comment on other site issues please do so on the Lantern Thread.  Thank you.    

 

Interest Posts:

 

FTJ means 'For the juniors' 

1)  Music report    thanks Dbg4thebest

2)  Number Puzzle - (thanks  Trincent)                                                 Thanks EinsterinJr   

3)  Last 2 digits of 5^2015                                                                   Thanks Radix and Melody

4)  How can you remember mean mode and median?                          Thanks MathsGod1 and anons

5)  Another circle special from Civonamzuk   (puzzle)                      Thanks anon

6)  A question regarding the forum (Thanks ShadowBolt04)                 Melody

7) Understanding polynomials and their roots                                       Thanks CPhill

8) Another polynomial question                                                            Thanks CPhill

9) Trig simultaneous equations                                                              Thanks Heureka and Melody

10) Given median, mean and restrictions, find range.       FTJ+             Melody

11) 2 taps filling a pool. Forget it, one tap is better.                           Thanks CPhill and Melody

 

                          ♫♪  ♪ ♫                                ♬ ♬ MELODY ♬ ♬                                 ♫♪  ♪ ♫

May 20, 2015
 #36
avatar+118723 
0

Thurs 21/5/15

If you would like to comment on other site issues please do so on the Lantern Thread.  Thank you.    

Interest Posts:

FTJ means 'For the juniors' 

1)  Music report3 presented by Dbg4thebest    

2)  What is best?  logic humour                             Thanks Anika121, CPhill and Dbg4thebest

3)  Fun with hemispheres                                      Thanks zacismyname, Melody, CPhill and Nauseated

4)  A little log manipulation                                    Melody

5)  A mystery to be solved by EinsteinJr                Thanks Chris

6)  Manipulating Trig                                              Melody

7)  Factoring - beware this is a very common error!   (middle high level)      Thanks CPhill

8)  Last 2 digits of 5^2015   (continued)                Thanks CPhill

9)  Another circle puzzle from Civonamzuk             Thanks Heureka

10) Difficult integration                                           Melody

 

                          ♫♪  ♪ ♫                                ♬ ♬ MELODY ♬ ♬                                 ♫♪  ♪ ♫

May 20, 2015
 #2
avatar+118723 
+5

2 taps A and B can fill a swimming pool in 3 hours. If turned on alone, it takes tap A 5 hours less than tap B to fill the same pool. How many hours does it take tap A to fill the pool?

 

A is the fast one:   let tap A take X hours to fill the pool

A fills 1 pool in X hours

that is 3 pools in 3X hours   OR      3/X pools in 3 hours

B fills 1 pool in X+5 hours

that is 3 pools in 3(X+5) hours    OR        3/(X+5) pools in 3 hours

So together in 3 hours they will fill

 

$$\frac{3}{X}+\frac{3}{X+5} \;\;pools\\\\
=\frac{3(X+5)+3X}{X(X+5)}\;\;pools\; in\; 3 \;hours\\\\
$But in 3 hours they fill 1 pool so $\\\\
\frac{3(X+5)+3X}{X(X+5)}=1\\\\
3(X+5)+3X=X(X+5)\\\\
3X+15+3X=X^2+5X\\\\
6X+15=X^2+5X\\\\
X^2+5X-6X-15=0\\\\
X^2-X-15=0\\\$$

 

$${{\mathtt{x}}}^{{\mathtt{2}}}{\mathtt{\,-\,}}{\mathtt{x}}{\mathtt{\,-\,}}{\mathtt{15}} = {\mathtt{0}} \Rightarrow \left\{ \begin{array}{l}{\mathtt{x}} = {\mathtt{\,-\,}}{\frac{\left({\sqrt{{\mathtt{61}}}}{\mathtt{\,-\,}}{\mathtt{1}}\right)}{{\mathtt{2}}}}\\
{\mathtt{x}} = {\frac{\left({\sqrt{{\mathtt{61}}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{1}}\right)}{{\mathtt{2}}}}\\
\end{array} \right\} \Rightarrow \left\{ \begin{array}{l}{\mathtt{x}} = -{\mathtt{3.405\: \!124\: \!837\: \!953\: \!327\: \!2}}\\
{\mathtt{x}} = {\mathtt{4.405\: \!124\: \!837\: \!953\: \!327\: \!2}}\\
\end{array} \right\}$$

 

Obviously the negative answer is invalid  so X = 4.4051 hours to fill the pool

 

$${\mathtt{60}}{\mathtt{\,\times\,}}{\mathtt{0.405\: \!1}} = {\mathtt{24.306}}$$

 

So that is near enough to 4 hours and 24 minutes

 

A will take 4 hours and 24 minutes to fill the pool

and

B will take 9 hours and 24 minutes to fill the pool.

May 20, 2015

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