Overclockers UK Forums > Life > General Discussion Noob ratio maths help

 29th Oct 2013, 11:16 #1 Lokai Capodecina     Joined: Jun 2008 Location: Wakefield Posts: 16,541 Noob ratio maths help Looking for a little assistance with a maths questions for someone that hasn't studied in 18 years - Taking two figures (380 ppm carbon dioxide and 1750 ppb methane), express the ratio of co2 to ch4 in the format x: 1, where x is a whole number given to two significant figures. If someone could point me in the right direction it would be greatly appreciated.
 29th Oct 2013, 11:19 #2 ~>Dg<~ Caporegime   Joined: Jun 2006 Location: Notts Posts: 26,422
 29th Oct 2013, 11:31 #3 dl8860 Wise Guy     Joined: Jul 2010 Location: W9 Posts: 1,285 If you divide the larger number by the smaller number when both are in equal units, the number you get is the 'x' you are looking for. Athlon II 640 | 6950 Asus TF300T | Nexus 6P
 29th Oct 2013, 11:39 #4 The Dread Pirate Capodecina     Joined: Aug 2007 Location: Outside in the bushes Posts: 15,794 Do Your own Damn Homework! Reach into your bag of tricks and pull another one...
 29th Oct 2013, 12:07 #5 rubberduck Wise Guy   Joined: Feb 2004 Posts: 2,362 1750 ppb = 1.75 ppm So 380/1.75 = 217.14 So i guess the answer is 217.14 : 1
 29th Oct 2013, 12:13 #6 Lokai Capodecina     Joined: Jun 2008 Location: Wakefield Posts: 16,541 Great, thanks for your help, i wasn't converting the methane to ppm from ppb which is where i was going wrong.
29th Oct 2013, 12:17   #7
Freakbro
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Quote:
 Originally Posted by rubberduck 1750 ppb = 1.75 ppm So 380/1.75 = 217.14 So i guess the answer is 217.14 : 1
Except it asks for a whole number to 2 significant figures, not 2 decimal places - which wouldn't be a whole number anyway.

So the answer would be 220 : 1

But well spotted on the ppb I hadn't noticed that

 29th Oct 2013, 12:36 #8 Rudeboy1 Hitman   Joined: Sep 2013 Posts: 520 567
29th Oct 2013, 14:04   #9
Spunkey
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Quote:
 Originally Posted by Freakbro Except it asks for a whole number to 2 significant figures, not 2 decimal places - which wouldn't be a whole number anyway. So the answer would be 220 : 1
Doesn't 'significant figures' mean 'integer', not nearest factor of 10? I made the answer 217:1

29th Oct 2013, 14:22   #10
Freakbro
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Quote:
 Originally Posted by Spunkey Doesn't 'significant figures' mean 'integer', not nearest factor of 10? I made the answer 217:1
No, significant figures means just that, the first set of numbers starting with one that is not zero, then you round up as normal.

So 655,464 to 3 significant figures would be 655,000
to 2 significant figures would be 660,000
and to 1 significant figure would be 700,000

Last edited by Freakbro; 29th Oct 2013 at 14:26.

 29th Oct 2013, 15:02 #11 Spunkey Capodecina     Joined: Oct 2002 Location: The land of milk & beans Posts: 12,529