# word problem help, converting measurements

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• Oct 22nd 2012, 05:01 AM
Tweety
word problem help, converting measurements
question 1) You need to give 1g of erythromycin orally. You have erythromycin suspension 250mg in 5ml. How much of the suspension do you need to give? ( 1000mg = 1g)

so we have 250mg in 5ml, and i need to give 1g,

so is it

$250 \times 4 = 1000$

so 1000mg = 20 ml?

So I need to give 20ml?

question 2) you are to administrator a drug to a patient that comes in strength 1 in 100, you need to give the patient 200mg of the drug. how man ml would you need to prepare? (1 in 1000 means 1g in 1000ml, )

Am not sure how to to this one,

if 1 in 100 means, 1g in 100ml, than 200mg is gong to be 0.2g in 20ml, so is it 20ml I need to give?

thank you,
• Oct 22nd 2012, 10:23 AM
MarkFL
Re: word problem help, converting measurements
You have found the correct answers. You may want to set up ratios to solve the problems, so that you have a method that is easy to use when you can't just "eyeball" the answers.

1.) $\frac{5}{250}=\frac{x}{1000}$

$\frac{1}{50}=\frac{x}{1000}$

$x=\frac{1000}{50}=20$

2.) $\frac{1}{100}=\frac{0.2}{x}$

$\frac{1}{100}=\frac{1}{5x}$

$5x=100$

$x=20$
• Oct 22nd 2012, 10:26 AM
bjhopper
Re: word problem help, converting measurements
Quote:

Originally Posted by Tweety
question 1) You need to give 1g of erythromycin orally. You have erythromycin suspension 250mg in 5ml. How much of the suspension do you need to give? ( 1000mg = 1g)

so we have 250mg in 5ml, and i need to give 1g,

so is it

you must define the concentration of what you have. $250 \times 4 = 1000$

so 1000mg = 20 ml?

So I need to give 20ml?

question 2) you are to administrator a drug to a patient that comes in strength 1 in 100, you need to give the patient 200mg of the drug. how man ml would you need to prepare? (1 in 1000 means 1g in 1000ml, )

Am not sure how to to this one,

if 1 in 100 means, 1g in 100ml, than 200mg is gong to be 0.2g in 20ml, so is it 20ml I need to give?

thank you,

you must define the concentration of your stock