Guest guest Posted September 23, 2003 Report Share Posted September 23, 2003 Dear Phbee-kcl, This is solved by using alligation method number two or Tutorial Alligation II. In fact it is the only way I have seen it solved. Please go to the Tutorial and try it. The tic tac toe will not type well on the posts. However you MUST know how much solution you are going to make. so go back to the problem and let us know. For example make 1 liter of this 12.5% solution. 20 % - 5% = 15 % This will be the denominator 12.5 - 5 = 7.5 % this will be the numerator of the parts of the 15 that are being used from the 20%. 20% - 12.5 = 7.5% this will be the numerator of the parts of the 15 that are being used from the 5% you now have 7.5 parts of the 15 whole x 1000 ml = 500 ml of 20% solution 7.5 parts of the 15 whole x 1000 ml = 500 ml of 5% solution Makes whole solution of 15 parts = 1000ml of a 12.5% solution Again this is MUCH BETTER explained in the Tutorial in the file section using the tic tac toe method. You may also notice that 12.5% is half way between 20% and 5%. So if you use one half of each the solution must be one half of each. So if you are making a 1000ml solution then use 1/2 of each or 500ml of each. Unfortunately not all of these can be solved this way. Hope this helps you out! Respectfully, Jeanetta Mastron CPhT F/O > Hi guys. Here's another math problem I can't figure out.. > > To process a prescription order for a 12.5% dextrose solution, the > pharmacy tech would mix the stock solutions of 20% dextrose and 5% > dextrose solutions in which ratio? > > Thanks in advance. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 23, 2003 Report Share Posted September 23, 2003 I check and it doesn't give you how much solution you are goign to make. What I wrote is exactly how it appears on the question.... and its on the PTCB practice exam. " To process a prescription order for a 12.5% dextrose solution, the pharmacy tech would mix the stock solutions of 20% dextrose and 5% dextrose solutions in which ratio " I even re-read it : ( I'm confuse. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 23, 2003 Report Share Posted September 23, 2003 You can still get the ratio without having a final volume given. Original setup is like: 20%..................?? ..........12.5%......... ...5%..................?? (Pretend it's a big X with the 12.5% in the center) The first set of math is: 20% - 12.5% = 7.5 5% - 12.5% = 7.5 So you then have 20%..............7.5 ..........12.5%....... ....5%.............7.5 (Again, pretend it's a big X with the 12.5% in the center) Now you read it as: You need 7.5 parts of the 20% solution to mix with 7.5 parts of the 5% solution to make the whole. So it is a 7.5:7.5 ratio, which then would work down to 1:1 ratio. Hopefully this makes sense? Della Cat Haven, Inc A No-Kill Cat Rescue Houston, Tx www.cat-haven.org -----Original Message----- From: phbee_kcl [mailto:phbee_kcl@...] I check and it doesn't give you how much solution you are goign to make. What I wrote is exactly how it appears on the question.... and its on the PTCB practice exam. " To process a prescription order for a 12.5% dextrose solution, the pharmacy tech would mix the stock solutions of 20% dextrose and 5% dextrose solutions in which ratio " I even re-read it : ( I'm confuse. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 23, 2003 Report Share Posted September 23, 2003 Wow, MUCH better! Thanks to all three of you for first asking the question and then posting the two replies. When you're first starting out you don't know quite what to ask. It really, really helps to have the problem worked out two times at least, each a slightly different way. I now know how to answer a question like this! And, I'm hopefully further down the road to a passing score on the exam. Thanks, again! Shel > You can still get the ratio without having a final volume given. > > Original setup is like: > 20%..................?? > .........12.5%......... > ..5%..................?? > > (Pretend it's a big X with the 12.5% in the center) > > The first set of math is: > 20% - 12.5% = 7.5 > 5% - 12.5% = 7.5 > > So you then have > > 20%..............7.5 > .........12.5%....... > ...5%.............7.5 > > (Again, pretend it's a big X with the 12.5% in the center) > > Now you read it as: > > You need 7.5 parts of the 20% solution to mix with 7.5 parts of the 5% > solution to make the whole. > > So it is a 7.5:7.5 ratio, which then would work down to 1:1 ratio. > > Hopefully this makes sense? > > Della > > Cat Haven, Inc > A No-Kill Cat Rescue > Houston, Tx > www.cat-haven.org > > -----Original Message----- > From: phbee_kcl [mailto:phbee_kcl@y...] > > I check and it doesn't give you how much solution you are goign to make. > What I wrote is exactly how it appears on the question.... and its on the > PTCB practice exam. > > " To process a prescription order for a 12.5% dextrose solution, the pharmacy > tech would mix the stock solutions of 20% dextrose and 5% dextrose solutions > in which ratio " > > I even re-read it : ( I'm confuse. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 23, 2003 Report Share Posted September 23, 2003 Thanks!!!!!! That helps alot : ) But how would you know if its a 1:2 ratio? > You can still get the ratio without having a final volume given. > > Original setup is like: > 20%..................?? > .........12.5%......... > ..5%..................?? > > (Pretend it's a big X with the 12.5% in the center) > > The first set of math is: > 20% - 12.5% = 7.5 > 5% - 12.5% = 7.5 > > So you then have > > 20%..............7.5 > .........12.5%....... > ...5%.............7.5 > > (Again, pretend it's a big X with the 12.5% in the center) > > Now you read it as: > > You need 7.5 parts of the 20% solution to mix with 7.5 parts of the 5% > solution to make the whole. > > So it is a 7.5:7.5 ratio, which then would work down to 1:1 ratio. > > Hopefully this makes sense? > > Della > > Cat Haven, Inc > A No-Kill Cat Rescue > Houston, Tx > www.cat-haven.org > > -----Original Message----- > From: phbee_kcl [mailto:phbee_kcl@y...] > > I check and it doesn't give you how much solution you are goign to make. > What I wrote is exactly how it appears on the question.... and its on the > PTCB practice exam. > > " To process a prescription order for a 12.5% dextrose solution, the pharmacy > tech would mix the stock solutions of 20% dextrose and 5% dextrose solutions > in which ratio " > > I even re-read it : ( I'm confuse. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 23, 2003 Report Share Posted September 23, 2003 Do the problem using a 15% and a 7.5% Dex solutions to get a 12.5% solution: 15%.................?? ...........12.5%....... 7.5%...............?? 15 - 12.5 = 2.5 7.5 - 12.5 = 5 So you'd use 2.5 parts of the 15% and 5 parts of the 7.5%, which would filter down to being 1 (2.5 divided by 2.5) parts of 15% and 2 (5 divided by 2.5) parts of 7.5% Now, extend the question. If you have the 15% and the 7.5% how much of each would you use to make 1 liter of 12.5% solution? Della Cat Haven, Inc A No-Kill Cat Rescue Houston, Tx www.cat-haven.org Re: Math ratio Thanks!!!!!! That helps alot : ) But how would you know if its a 1:2 ratio? Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 23, 2003 Report Share Posted September 23, 2003 Dear Phbe_Kcl, Actually it is my fault that I stated that you need the volumme to make. I 'read' or interpreted the questionwrong. I read or interpreted how much of each the 20% and th 5% do you need. That would have been an alligation and it would have required the amount or volumne that you need to make. However, YOU and DELLA are right the question asks for the 'ratio' of each not the volumes of each. In this case you would do the same thing and come up with 7.5 : 7.5 which is a 1 to 1 ratio or 1:1 Your second question was also addressed by Della, how do you doit if it is 1:2 or how would you know. Well if you did the subtraction and you get an answer that is a number that is half of the second number . So ifyou get an answer like : 3: 6 then that is a 1:2 or 3:9 then that is 1:3 but remember if it is backwards like: 9:3 then the ratio is 3:1 So it is said solution A is 3 to solution B 1 or 3 to 1 or 3:1 I hope this helps you. Be sure that you have the numbers inthe correct order. Resepctfully, Jeanetta > I check and it doesn't give you how much solution you are goign to > make. What I wrote is exactly how it appears on the question.... and > its on the PTCB practice exam. > > " To process a prescription order for a 12.5% dextrose solution, the > pharmacy tech would mix the stock solutions of 20% dextrose and 5% > dextrose solutions in which ratio " > > I even re-read it : ( I'm confuse. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 23, 2003 Report Share Posted September 23, 2003 Shel, Glad to have been some hep even with not rading the question right for a ratio instead of volume. Thanks Jeanetta > > You can still get the ratio without having a final volume given. > > > > Original setup is like: > > 20%..................?? > > .........12.5%......... > > ..5%..................?? > > > > (Pretend it's a big X with the 12.5% in the center) > > > > The first set of math is: > > 20% - 12.5% = 7.5 > > 5% - 12.5% = 7.5 > > > > So you then have > > > > 20%..............7.5 > > .........12.5%....... > > ...5%.............7.5 > > > > (Again, pretend it's a big X with the 12.5% in the center) > > > > Now you read it as: > > > > You need 7.5 parts of the 20% solution to mix with 7.5 parts of > the 5% > > solution to make the whole. > > > > So it is a 7.5:7.5 ratio, which then would work down to 1:1 ratio. > > > > Hopefully this makes sense? > > > > Della > > > > Cat Haven, Inc > > A No-Kill Cat Rescue > > Houston, Tx > > www.cat-haven.org > > > > -----Original Message----- > > From: phbee_kcl [mailto:phbee_kcl@y...] > > > > I check and it doesn't give you how much solution you are goign to > make. > > What I wrote is exactly how it appears on the question.... and its > on the > > PTCB practice exam. > > > > " To process a prescription order for a 12.5% dextrose solution, > the pharmacy > > tech would mix the stock solutions of 20% dextrose and 5% dextrose > solutions > > in which ratio " > > > > I even re-read it : ( I'm confuse. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 23, 2003 Report Share Posted September 23, 2003 Thanks Della, must have had a brain freeze in the middle of reading that question. J > You can still get the ratio without having a final volume given. > > Original setup is like: > 20%..................?? > .........12.5%......... > ..5%..................?? > > (Pretend it's a big X with the 12.5% in the center) > > The first set of math is: > 20% - 12.5% = 7.5 > 5% - 12.5% = 7.5 > > So you then have > > 20%..............7.5 > .........12.5%....... > ...5%.............7.5 > > (Again, pretend it's a big X with the 12.5% in the center) > > Now you read it as: > > You need 7.5 parts of the 20% solution to mix with 7.5 parts of the 5% > solution to make the whole. > > So it is a 7.5:7.5 ratio, which then would work down to 1:1 ratio. > > Hopefully this makes sense? > > Della > > Cat Haven, Inc > A No-Kill Cat Rescue > Houston, Tx > www.cat-haven.org > > -----Original Message----- > From: phbee_kcl [mailto:phbee_kcl@y...] > > I check and it doesn't give you how much solution you are goign to make. > What I wrote is exactly how it appears on the question.... and its on the > PTCB practice exam. > > " To process a prescription order for a 12.5% dextrose solution, the pharmacy > tech would mix the stock solutions of 20% dextrose and 5% dextrose solutions > in which ratio " > > I even re-read it : ( I'm confuse. Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 23, 2003 Report Share Posted September 23, 2003 15% 5 X X=667 --- = --- 7.5 1000mL 7.5% 2.5 X X=333 ----- = ----- 7.5 1000mL To compound this prescription, 667mL of 15% is added to 333mL of 7.5mL to make 1 L of 12.5% solution I hope I did it correct :/ > Do the problem using a 15% and a 7.5% Dex solutions to get a 12.5% solution: > > 15%.................?? > ..........12.5%....... > 7.5%...............?? > > 15 - 12.5 = 2.5 > 7.5 - 12.5 = 5 > > So you'd use 2.5 parts of the 15% and 5 parts of the 7.5%, which would > filter down to being 1 (2.5 divided by 2.5) parts of 15% and 2 (5 divided by > 2.5) parts of 7.5% > > Now, extend the question. If you have the 15% and the 7.5% how much of > each would you use to make 1 liter of 12.5% solution? > > Della > > Cat Haven, Inc > A No-Kill Cat Rescue > Houston, Tx > www.cat-haven.org > > Re: Math ratio > > > Thanks!!!!!! That helps alot : ) But how would you know if its a 1:2 > ratio? Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 24, 2003 Report Share Posted September 24, 2003 Yup, you got the right answer. Also, if you already have the ratio (1:2). You have a total of 3 parts. Since it is 1 part of Solution A and 2 parts of Solution B. So you can take 1000 mL, divide it by 3, and you get 333.3 mL per part. Since Solution A is 1 part, it would use the 333.3 mL (1 part x 333.3 mL/part). Since Solution B is 2 parts, it would use 666.7 (2 parts x 333.3 mL/part). Then you add the two volumes (Solution A: 333.3 mL, Solution B: 666.7 mL, together they equal 1000 mL) to check that you do have enough volume (1000 mL) that was being asked for. There's always different ways of working things out. Everyone has to find what works for them. If you have one that is a ratio of 3:2, then you would have a total of 5 parts. So 1000 mL divided by 5 gives you 200 mL per part. Then Solution A would be 3 * 200ml or 600ml and Solution B would be 2 * 200ml or 400 mL. When you add the volume of the parts (600mL of Solution A plus 400mL of Solution you get 1000 mL total volume, which is your check. Della Cat Haven, Inc A No-Kill Cat Rescue Houston, Tx www.cat-haven.org Re: Math ratio To compound this prescription, 667mL of 15% is added to 333mL of 7.5mL to make 1 L of 12.5% solution I hope I did it correct :/ Quote Link to comment Share on other sites More sharing options...
Guest guest Posted September 24, 2003 Report Share Posted September 24, 2003 My approach to this is the allegation method. In the allegation method, the larger % strength is located in the upper left, the desired strength is in the middle column, and the smaller strength is located in the lower left. subtract diagonally to find the parts of each solution. Add the parts to get the total parts. Then set each part equal to the total quantity desired and solve for x. In this problem, you were asked for the ratio only. You do not have to find the total volume of each part. 20 7.5 12.5 5 7.5 ___ total parts 15 So the ratio is 1:1 Quote Link to comment Share on other sites More sharing options...
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