Math geeks all hands on deck!

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Aug 2, 2009
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#21
You can't really add those unless they has a common de-nom-nom-inator :rolleyes:

So 1/8 = 3/24..

So 1/24 + 3/24 = 4/24

and we all know that 4/24 is just a fancy name for 6 :)
I actually did that wrong :/

4/24 = 1/6, not 6.
 
F

FireWire

Guest
#22
I think it's 8 hours because it took too long for the other faucet to fill up so it got turned off HEHE.
 

JGuy

Junior Member
Apr 18, 2013
28
0
1
#25
[...]
You have one faucet that fills up a pool in 24 hours.
You have second faucet that fills up a pool in 8 hours.
If you run both faucets in one pool, how long does it take to fill up the pool?

I figured out i was approaching the answer wrong. So now i understand where i went wrong. Now i just can't figure out the math to the correct logical approach. So now i understand how to get to the correct answer, I just don't know the math itself.

Will be fun to see everyones answers either way.
Seems to me that one logical approach is to determine the combined fill rates, and then work backwards from that rate to determine the time to fill one pool.

For example, the two fill rates are: 1 pool per 24 hours, and 1 pool per 8 hours. Combined, the math is 1/24 + 1/8 = 4/24. In human speak, that means the combined fill rate is 4 pools can be filled every 24 hours. Simplified to 1 pool, that's 1 pool filled every 6 hours.
 
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seoulsearch

OutWrite Trouble
May 23, 2009
16,440
5,387
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#26
I just wanted to say how much I really enjoyed this thread!!

Although it's obvious I'm not attempting to answer the question (cough, cough :rolleyes:), it's really a lot of fun and quite interesting to read how people have come up with the answer. Unfortunately, math taps into the part of my brain that either isn't there or just doesn't work.

But I think this would be an awesome idea for a regular thread series: "Math Problem of the Week" or general problems that people could offer their solutions to... (Wallpapering? Changing out the hardware in the back of your toilet? Keeping plants alive? Not that any of this would apply to me... Again... cough, cough, cough.)

It was just really cool to see everyone dig in and come up with their own answers. Even the non-math-related ones! :)
 
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JimJimmers

Senior Member
Apr 26, 2012
2,592
76
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#27
I took out my note pad and did the maths problem myself.

I ended up with: "Donuts".

Wrong, I'm afraid. The correct response was: "Pancakes."

Better luck next time.
 

JimJimmers

Senior Member
Apr 26, 2012
2,592
76
48
#28
Assume that the pool is 48 gallons.

Faucet 1 must be running at 2 gallons per hour. (48 / 24 = 2)

Faucet 2 must be running at 6 gallons per hour. (48 / 8 = 6)

So if you run them both, you have a flow of 8 gallons per hour (2 + 6 = 8), therefore it would take 6 hours to fill up the pool. (8 * 6 = 48)

...Am I right?

As a veteran house remodel-er, and a decent plumber, I must protest the ruling. (I am sure Oncefallen will back me up on this)

We have to know the pipe setup, to know if both faucets will pump at their individual capacity when both are on. We'll need to see the pump rating as well, if the swimming pool isn't on a water main.

Also, the rate of evaporation is a constant, assuming constant temperature and humidity. Therefore the two faucets will fill faster than the combined capacity.
 
K

kenthomas27

Guest
#29
This would've been my test paper. I was pretty lucky with answers sometimes...

Math test.jpg
 

Attachments

seoulsearch

OutWrite Trouble
May 23, 2009
16,440
5,387
113
#30
^^^ Kenthomas, in the 5 years I've been here...

This would definitely be on my list of 5 Best Posts I've Ever Seen On CC!!!

I'm still laughing!!! :)
 
A

Arlene89

Guest
#31
We seriously need a random comic strip or drawing thread where we respond to each other in silly drawings. Kenthomas, that was hilarious.
 

posthuman

Senior Member
Jul 31, 2013
37,788
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#32
the correct answer is already posted but being a math geek, i want to work it out for myself too :)

let x be the rate of the first faucet, y the rate of the second faucet, in units-per-hour
and let z be the volume of the pool in units.

then 24*x = z = 8*y

so x = z/24
and y = z/8

let t be the time it takes to fill up the pool with both faucets.

then

x*t + y*t = z
or making substitutions,
(z/24)*t + (z/8)*t = z

z*(1/24 +1/8) = z/t

(1/24 + 3/24) = 1/t

4/24 = 1/6 = 1/t

t = 6 hours


 
T

todo

Guest
#33
i like how everyone assumed the pools are either the same pool or of the same size, but neither were said. so depending on your assumptions, this probolem is unsolvable
 

posthuman

Senior Member
Jul 31, 2013
37,788
13,546
113
#36
i like how everyone assumed the pools are either the same pool or of the same size, but neither were said. so depending on your assumptions, this probolem is unsolvable
i'd like to rephrase my answer in terms of an "unit pool"

from there, it's trivially only a scaling problem using the unitless volumetric ratio of (any given pool)/(unit pool)
 

posthuman

Senior Member
Jul 31, 2013
37,788
13,546
113
#37
let the engineers sort that out lol; this is a math problem

;)
 

Oncefallen

Idiot in Chief
Staff member
Jan 15, 2011
6,061
3,407
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#38
As a veteran house remodel-er, and a decent plumber, I must protest the ruling. (I am sure Oncefallen will back me up on this)

We have to know the pipe setup, to know if both faucets will pump at their individual capacity when both are on. We'll need to see the pump rating as well, if the swimming pool isn't on a water main.

Also, the rate of evaporation is a constant, assuming constant temperature and humidity. Therefore the two faucets will fill faster than the combined capacity.
As I was reading through this thread this type of post was on my mind. I burst out laughing when I saw that someone beat me to it.
 
I

iTOREtheSKY

Guest
#39
So,I was thinking.....

(not really)


rage-maths.jpg
 

seoulsearch

OutWrite Trouble
May 23, 2009
16,440
5,387
113
#40
As a veteran house remodel-er, and a decent plumber, I must protest the ruling. (I am sure Oncefallen will back me up on this)

We have to know the pipe setup, to know if both faucets will pump at their individual capacity when both are on. We'll need to see the pump rating as well, if the swimming pool isn't on a water main.

Also, the rate of evaporation is a constant, assuming constant temperature and humidity. Therefore the two faucets will fill faster than the combined capacity.
As I was reading through this thread this type of post was on my mind. I burst out laughing when I saw that someone beat me to it.

Leave it to the Jim's!!!

"Wonder Jim Powers, ACTIVATE!!! Form of, Professional Contractor! Shape of, Evaporation Expert Extraordinaire!"