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Cistern

by harsh.champ » Wed Feb 17, 2010 4:28 am
Two taps can fill a cistern in 8 hours and 16 hours respectively and another 3rd tap can empty it in 12 hours.If all three are opened simultaneously,what proportion of the cistern is filled in 6 hours?

(A)1/2
(B)1/4
(C)5/6
(D)3/4
(E)5/8


Note:-Read the question very carefully.:)
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by money9111 » Wed Feb 17, 2010 7:32 am
IMO A
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by Osirus@VeritasPrep » Wed Feb 17, 2010 7:37 am
choose E

You need to add the rates of the two filling the tank and subtract the rate of the thing that is emptying it.

You get 3/16 - 1/12 which equals 5/48

multiply this rate by 6 hours, and you get 30/48. Reduce this and you get 5/8
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by shashank.ism » Wed Feb 17, 2010 7:40 am
harsh.champ wrote:Two taps can fill a cistern in 8 hours and 16 hours respectively and another 3rd tap can empty it in 12 hours.If all three are opened simultaneously,what proportion of the cistern is filled in 6 hours?

(A)1/2
(B)1/4
(C)5/6
(D)3/4
(E)5/8


Note:-Read the question very carefully.:)
in 1 hour
1st tap fill = 1/8
2nd tap fill = 1/16
3rd tap empty = 1/12
total fill = 1/8 + 1/16 -1/12 = 5/48
In 6 hours = 5/48 x 6 = [spoiler]5/8 Ans E money how did u got A please clarify..[/spoiler]
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by Osirus@VeritasPrep » Wed Feb 17, 2010 7:43 am
shashank.ism wrote:
harsh.champ wrote:Two taps can fill a cistern in 8 hours and 16 hours respectively and another 3rd tap can empty it in 12 hours.If all three are opened simultaneously,what proportion of the cistern is filled in 6 hours?

(A)1/2
(B)1/4
(C)5/6
(D)3/4
(E)5/8


Note:-Read the question very carefully.:)
in 1 hour
1st tap fill = 1/8
2nd tap fill = 1/16
3rd tap empty = 1/12
total fill = 1/8 + 1/16 -1/12 = 5/48
In 6 hours = 5/48 x 6 = [spoiler]5/8 Ans E money how did u got A please clarify..[/spoiler]
I would guess that he didn't copy and paste the answer from complore like you did, but I don't know.
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by money9111 » Wed Feb 17, 2010 7:48 am
I was going to go that route but decided to just average them... clearly not the best option but now I know for next time... so basically for all rate problems add them together by finding the LCD and then reduce etc etc
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by shashank.ism » Wed Feb 17, 2010 7:50 am
osirus0830 wrote:
I would guess that he didn't copy and paste the answer from complore like you did, but I don't know.
ok keep posting such things ..its your wish..
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by Osirus@VeritasPrep » Wed Feb 17, 2010 7:51 am
money9111 wrote:I was going to go that route but decided to just average them... clearly not the best option but now I know for next time... so basically for all rate problems add them together by finding the LCD and then reduce etc etc

You'll get to it when you do the Word Translations guide. Basically you treat the work problems like Distance Rate and Time problems

For example, the only real difference is that the distance is replaced by "work." So after you find the rates you just set up the equation Work = Rate X Time and you solve for whichever variable you need.
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by shashank.ism » Wed Feb 17, 2010 7:58 am
osirus0830 wrote:
money9111 wrote:I was going to go that route but decided to just average them... clearly not the best option but now I know for next time... so basically for all rate problems add them together by finding the LCD and then reduce etc etc

You'll get to it when you do the Word Translations guide. Basically you treat the work problems like Distance Rate and Time problems

For example, the only real difference is that the distance is replaced by "work." So after you find the rates you just set up the equation Work = Rate X Time and you solve for whichever variable you need.
Mathematically,
step 1: Just reciprocate the "time" and give + for filling and - for emptying. you will get value for 1 hour
step2: multiply it by time for the time required. you get the answer.
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by money9111 » Wed Feb 17, 2010 8:05 am
I'll look forward to word translations then lol because right now I feel dumb that i mix them up! :-/
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by Osirus@VeritasPrep » Wed Feb 17, 2010 8:06 am
money9111 wrote:I'll look forward to word translations then lol because right now I feel dumb that i mix them up! :-/
No worries, after this weekend's Veritas math class, I will post their method for attacking these problems as well, so the board will be equipped with the two best approaches :)
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by cunazza » Wed Feb 17, 2010 8:15 am
harsh.champ wrote:Two taps can fill a cistern in 8 hours and 16 hours respectively and another 3rd tap can empty it in 12 hours.If all three are opened simultaneously,what proportion of the cistern is filled in 6 hours?

(A)1/2
(B)1/4
(C)5/6
(D)3/4
(E)5/8


Note:-Read the question very carefully.:)
Tap A does 1/8 of the work in 1 hour. Tap B does 1/16 of the work in 1 hour. Tap C does 1/12 of ITS work in 1 hour.
Overall Rate = 1/8 + 1/16 - 1/12 = 5/48 (it is -1/12 because the tap C EMPTIES the pool). Multiplies this value by 6 hours and we get 5/8.
In my opinion the right choice is E.
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by money9111 » Wed Feb 17, 2010 8:19 am
harsh.champ i just realized that the OA is not provided... it's clear what it is.. but can you post it anyway?

shashank.ism - i simply took the overall average...
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by shashank.ism » Wed Feb 17, 2010 8:30 am
money9111 wrote:harsh.champ i just realized that the OA is not provided... it's clear what it is.. but can you post it anyway?

shashank.ism - i simply took the overall average...
I think u can ask original ans from osirus. He just found it out on complore as he stated above...how would u reach to the ans by just taking average..would u elaborate ur answer in mathematical form..I am not getting your solution money...please elaborate...
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by Osirus@VeritasPrep » Wed Feb 17, 2010 8:33 am
shashank.ism wrote:
money9111 wrote:harsh.champ i just realized that the OA is not provided... it's clear what it is.. but can you post it anyway?

shashank.ism - i simply took the overall average...
I think u can ask original ans from osirus. He just found it out on complore as he stated above...how would u reach to the ans by just taking average..would u elaborate ur answer in mathematical form..I am not getting your solution money...please elaborate...
LOL...actually complore is blocked by websense during market hours at my firm. I actually know how to do these troll.
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