Please help with maaaaaaths

Mr. McGreg

If I have a 2% solution of a substance in 2ml of water and add it to a 2% solution of of the same substance in 2 ml of water do I get a 2% solution of that substance in 4ml of water? Can some please explain the maths behind this, my mind won't work for some reason.

I work as a scientist.....

rob w

Mr. McGreg wrote: »

If I have a 2% solution of a substance in 2ml of water and add it to a 2% solution of of the same substance in 2 ml of water do I get a 2% solution of that substance in 4ml of water? Can some please explain the maths behind this, my mind won't work for some reason.

I work as a scientist.....

You study science you mean?

Mr. McGreg

rob w wrote: »

You study science you mean?

Oh no I've already done that, I'm a bona fide scientist (these are my burning questions)

ponzook

Dam you!

spock.

2% of 2ml is 0.04ml. So the 2ml contains 0.04ml solute and 1.96ml water.

Add this to itself and you get 4ml containing 1.96(2) = 3.92ml water and 0.04(2) = 0.08ml solute.

0.08 is 2% of 4.0 so the concentration is still 2%

Mehaffey1

2/100 + 2/100 = 4/200

4/200 divided by 2 to get back to percentage equals 2%

...I work as farm worker lol

Pherekydes

Mehaffey1 wrote: »

2/100 + 2/100 = 4/200

Since when?

Has arithmetic changed this much since the '60s?

Mr. McGreg

spock. wrote: »

2% of 2ml is 0.04ml. So the 2ml contains 0.04ml solute and 1.96ml water.

Add this to itself and you get 4ml containing 1.96(2) = 3.92ml water and 0.04(2) = 0.08ml solute.

0.08 is 2% of 4.0 so the concentration is still 2%

Thanks that's exactly the maths logic I was looking for, knew the answer but like a real (crap) scientist, spent ages trying to remember why.

Moody_mona

Mehaffey1 wrote: »

2/100 + 2/100 = 4/200

4/200 divided by 2 to get back to percentage equals 2%

...I work as farm worker lol

Not exactly.

The maths is explained above by spock.

There's more solution in the 4ml sample but the concentration hasn't changed. The glass of wine and the bottle of wine are both 12% abv; they're different volumes and different quantities of alcohol, but comparatively speaking, the concentration is the same.

Second Toughest in_the Freshers

Until you finish the glass, that is.

Mr. McGreg

Mehaffey1 wrote: »

2/100 + 2/100 = 4/200

4/200 divided by 2 to get back to percentage equals 2%

...I work as farm worker lol

I get what you're trying to say there, but in fraction terms 2/100 + 2/100 = 4/100 so it doesn't work! Looks like science trumps farming this round...just about! Cheers for answering anyway

simdan

Mr. McGreg wrote:

Thanks that's exactly the maths logic I was looking for, knew the answer but like a real (crap) scientist, spent ages trying to remember why.

Remember why?? It's basic maths, surely you need basic maths to become a scientist?

Mehaffey1

Mr. McGreg wrote: »

I get what you're trying to say there, but in fraction terms 2/100 + 2/100 = 4/100 so it doesn't work! Looks like science trumps farming this round...just about! Cheers for answering anyway

Multiply the top and bottom of the fraction by two then lol. It's one of those things were you know the answer but it's hard to explain how

Mr. McGreg

simdan wrote: »

Remember why?? It's basic maths, surely you need basic maths to become a scientist?

I work in biological science so basic maths isn't something I've ever regularly needed or will need! No excuse for not knowing this, but as good a reason as any