hmm.. maths help again..
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am here back to bug u maths xperts with with another maths question again..
thanks in advance,
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tats easy.. i leave it to other forumer to teach u..
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tats easy.. i leave it to other forumer to teach u..Originally posted by mr_sotong:tats easy.. i leave it to other forumer to teach u.. -
fer those who wld bother to help out.. just to double check.. my ans is 280g..
cheers
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tats easy.. i leave it to other forumer to teach u..Originally posted by bryanseb:tats easy.. i leave it to other forumer to teach u.. -
chimnology. give me 5min. i recall my throwaway a math skills to apply to this qn.
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I may be wrong, but here's what i think...
90 litres = 90 grams of salt.
It is gaining 2 grams of salt/min (gaining 4 litres/min - losing 3 litres/min)
It will take another 30 mins to fill the tank.
90 + (30 * 2) = 150 grams. -
Yeah, you're wrong alright.Originally posted by DailyFreeGames.com:I may be wrong, but here's what i think...
90 litres = 90 grams of salt.
It is gaining 2 grams of salt/min (gaining 4 litres/min - losing 3 litres/min)
It will take another 30 mins to fill the tank.
90 + (30 * 2) = 150 grams. You forgot to take into account that the initial volume had 1g of salt per litre. -
My solution might be acceptable for pri/sec levels, but i don't think it works for higher levels because the salt levels going in is more concentrated as time goes, so we can't simply assume it's gaining 2 gram salt per min as the solution gets more concentrated, when it's losing the mixture at 3 litres/min, a higher concentration of salt gets leaked out, which is why we can't assume it to be gaining 2 gram/min, but i guess if pri/sec school, they won't care so much.
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Aiyah, the 90 litres = 90 grams of salt is the initial volume mah...Originally posted by ditzy:Yeah, you're wrong alright. You forgot to take into account that the initial volume had 1g of salt per litre. -
tank got 90g of salt initially.
den tap turns on while drain got turned on too. overall gain 1litres/min
max cap. for tank is 120litres. so it will takes 30mins to fill the tank.
1st min,
IN: 94litres of salt water, 98g of salt
OUT: 91litres of salt water, 94.87234043g of salt.
2nd min,IN: 95litres of salt water, 102.8723404g of salt
OUT: 92litres, 99.6237402g
3rd
IN 96litres, 107.62.....g
OUT 93litres, 104.260....g
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30th min
IN 123litres lol lost count
OUT 120litres lol lost count -
12am:90 litre urine, 90g salt.
it say leakin at 3litre/min, so we assume that the 3 litre/min is all 1g of salt per L?
since there is 30more Litres to make the tank full.
leaking 3L/min, fill 4L/min is as good as filling in 1L/min
in other words is as good as leaking out 3G salt, fill in 8G salt/min.
5G salt gain /min.
30More litres to fill full the tank require 30mins since the replacment rate is 1L/min.
8G-3g*30mins=150 Grams
12.30am: moreover frm the inital it is 90grams ma. and it leak out 3L/min so actually all the initial 90litre urine, 90g salt are drained. and fulled by 2G/L urine. -
-____________-Originally posted by ChairmanJay:tank got 90g of salt initially.
den tap turns on while drain got turned on too. overall gain 1litres/min
max cap. for tank is 120litres. so it will takes 30mins to fill the tank.
1st min,
IN: 94litres of salt water, 98g of salt
OUT: 91litres of salt water, 94.87234043g of salt.
2nd min,IN: 95litres of salt water, 102.8723404g of salt
OUT: 92litres, 99.6237402g
3rd
IN 96litres, 107.62.....g
OUT 93litres, 104.260....g
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30th min
IN 123litres lol lost count
OUT 120litres lol lost count
if really need to count with "well-stir mixture"
and ure in secondary school lvl.
instead of using ontop method muz ownself come out wif a formula lor. -
i know la jc maths.Originally posted by carlsonxjd:-____________-
if really need to count with "well-stir mixture"
and ure in secondary school lvl.
instead of using ontop method muz ownself come out wif a formula lor.
i got the formula liao. i lazy to write out.
btw i'm not jc yet. so i'm using sec sch method. -
gosh e math.. try writing out the statistics.. may help for similar qns.. the qn's pretty easy
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Initially, 90 litres = 90 grams salt.
Water with salt conc. 2g/L flows into tank at 4L/min.
Drained at 3L/min.
Thus, 1L of 2g/L is added to the tank per minute.
At the 91th minute, tank should contain 92g salt with 91 litres.
1L gained = 2g salt gained.
Amount of salt when tank full = (120 - 90) X 2 + 90
150g
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Originally posted by carlsonxjd:12am:90 litre urine, 90g salt.
it say leakin at 3litre/min, so we assume that the 3 litre/min is all 1g of salt per L?
since there is 30more Litres to make the tank full.
leaking 3L/min, fill 4L/min is as good as filling in 1L/min
in other words is as good as leaking out 3G salt, fill in 8G salt/min.
5G salt gain /min.
30More litres to fill full the tank require 30mins since the replacment rate is 1L/min.
8G-3g*30mins=150 Grams
12.30am: moreover frm the inital it is 90grams ma. and it leak out 3L/min so actually all the initial 90litre urine, 90g salt are drained. and fulled by 2G/L urine.
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Originally posted by polarsnake:
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ok, i in sec 3, and i failed maths but dunno this can help abit or not:
tank capacity: 120 litre
initially->90litres of salt solution & 90g of salt (info 1)
then, 2g of salt/litre is flowing in @ 4litres/minute, thus, 1 minute, there is 4litre or salt solution, and 8g of salt(info2)
after that, some idiot go and on the drainage pipe, then it starts draining the salt solution at 3litres/minute.
how much salt does it contains when it is full?
in 3 minute, 90l+4l&90g+8g then minus the rate @ 3L/minute, that means...
AIYA I DUNNO�@LAR!!!!
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this question requires the use of calculus, you can't solve it using the normal rate x time method...uni maths leh!
becos most of you fail to realise that the mixture is well stirred and hence the concentration of salt in the tank is always changing and hence the amount of salt drained out will change every second. -
What module is this?
Paiseh, I very bad at making the starting equation. -
nostalgic question
must use add. maths calculus
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i believe this is an add.maths statistic qns..u need to form a formula first then with the formula solve the qns..
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MA1505.. past year paper
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i try and help... but may be wrong as i haven learn this in my sch...Originally posted by papercut87:
First of all, find the time need for the tank to be full...
"A tap is turn on and salt solution of 2g/L at 4L/min"
i guess you understand this sentence...
120L-90L=30L (amount needed of solution to be full)
4L/min - 3L/min = 1L/min (the tank will gain 1L/min of water...)
so to have 30L of water, we need 30min...
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"the WELL-STIRRED mixture" let just assume that there is magic here, and when the solution flow down, the whole mixture is mix...
"flow out of the tank at a rate of 3L/min" i guess you can understand this sentence...
every time, the amount of salt is different, now to find the speed of salt added...
since one min the will be 4L and 1L have 2 gram of salt, the speed of salt add is 4g/min
2g/L so 8g/4L
4L/min so 8g/min...
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next we need to find the speed of salt lost... this is the biggest problem as the amount of salt in water in different in every second, 1/2 second, 1/4 second~~...
up til here is dunno liao...