Can you check these calculations please?

[purplecatfish]

Maths Question:

The medication concentration is 4%,

And a final concentration of 0.1 mg/L is needed,

The Tank is 200L,

Is the dose A) 0.5ml or B) 5ml

[jim r]

IMO B as .1 is 1/40 of 4 and 200 divided by 40 = 5

[alanmin4304]

.4 x .01 x 200000 = 0.5

= 0.5mls

That is what comes from using the other side of the brain. Go lefty.

What are you dosing?

[Dixon1990]

i got 5 aswel

[Guest]

I got 0.5 aswell

[alanmin4304]

Cam, how did you get 0.5

[tHEcONCH]

.4 x .01 x 200000 = 0.5

= 0.5mls

That is what comes from using the other side of the brain. Go lefty.

What are you dosing?

Hang about - 0.4 is 40%, not 4%, and by 'concentration is 4%', do you mean that what you are using contains 4% of what you want to get up to 0.1/litre? If so, then shouldn't the calc be:

(0.1 x 200)

_________

4

x 100

= 500?

If not, then "0.04 x .01 x 200 = 0.8

[Guest]

Sorry I just done mine again and got 0.8. I done:

200 divide 4% = 8

8 x 0.1 = 0.8

[Dixon1990]

Hang about - 0.4 is 40%, not 4%, and by 'concentration is 4%', do you mean that what you are using contains 4% of what you want to get up to 0.1/litre? If so, then shouldn't the calc be:

(0.1 x 200)

_________

4

x 100

= 500?

If not, then "0.04 x .01 x 200 = 0.8

This is what i got the first 2 times.

[Slightly Blue Dalmation]

4% of what? what would 100% concentration of the medication be? 1mg or what? cos without that the 4% doesnt mean much

[tHEcONCH]

And a final concentration of 0.1 mg/L is needed,

The Tank is 200L,

0.1 x 200 = 20mg needed

The medication concentration is 4%

20 devided by 0.04 = 500

[Slightly Blue Dalmation]

without medication conc it doesnt mean much cos it could be 4% of any concentration there should be some total concentration on the bottle somewhere

[tHEcONCH]

I'm assuming that he means that whatever he has contains 4% of what he wants to get to a level of 0.1mg/litre. It might be a false assumption - he'll need to clarify what he means.

[Slightly Blue Dalmation]

from how it reads he wants .1mg/l in 200L but has, but the 4%conc sounds like the stuff he wants is 4% of the total bottle concentration of all the stuff in the bottle

[Dixon1990]

How much is in the bottle?

[Dixon1990]

I got 5ml again.

[Slightly Blue Dalmation]

exactly the 4% could be of any total concentration. so have to see what bottle says before can make accurate calculation

[Dixon1990]

5ml

[Slightly Blue Dalmation]

without clarification of what the 4% is of it means not a lot, im sure i learnt something from 3 years of chem at uni

[tHEcONCH]

Not where the 4% is the concentration of the medication required. We know he wants 20mg total (to get 0.1mg/litre in a 200 litre tank), so if the substance he has (I'm guessing its Formalin) is '4%', then all you need to do is devide the total quantity he need (20) by the percentage concentration (0.04).

[Dixon1990]

Does it not just mean its been diluted to 4%?

[tHEcONCH]

Ha, fast edit huh? In answer to your original post, Yes, diluted to 4%, which is what the above calculation assumes. If it was undiluted, he'd just use 20mg in a 200 litre tank to get 0.1mg/litre (20 devided by 200)

[Slightly Blue Dalmation]

the 4% doesnt tell how many mg are in the bottle, yeah he wants 20mg but that doesnt change the fact that dont know how much is in the bottle

[Dixon1990]

So that wuld meal 5mg right?

[alanmin4304]

4% is normally 4%w/v, which is 4 grams/litre

Try

4% x .1% x 200000

= 0.05mls of 4%

Too late--fish are dead.