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Solution

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In order to calculate the amount of drug in ml, you need to use the following formula:

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$\\dfrac{\\text{Prescribed dose}}{\\text{Stock Strength}}$ $\\times$ Stock dose.

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In this question: Prescribed dose is $\\var{a}$mg, Stock Strength is $\\var{b}$mg and Stock dose is 1ml.

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Using the formula: $\\dfrac{\\var{a}}{\\var{b}}$ $\\times$ $1$ = $\\var{c}$ml.

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Alternative Solution

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You are told that the stock strength of the drug is $\\var{b}$mg in $1$ml.

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So for every $\\var{b}$mg of the drug we need, we need to give the patient $1$ml.

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This means $\\var{b}$mg = 1ml.

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We need $\\var{a}$mg.

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In order to get $\\var{a}$mg, we divde $\\var{b}$mg by $\\var{d}$.

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Because $\\var{b}$mg = $1$ml and we have divided $\\var{b}$mg by $\\var{d}$ to get $\\var{a}$mg, we must divide the right hand side of the equals sign by $\\var{d}$ also.

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So, we have $\\dfrac{\\var{b}}{\\var{d}}$ = $\\dfrac{1}{\\var{d}}$.

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$\\var{a}$ = $\\var{c}$ml.

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Therefore we must need to give the patient $\\var{c}$ml.

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Question on drug calculations

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Your patient has been prescribed $\\var{a}$ mg of a drug as an injection. The stock strength given is $\\var{b}$mg in $1$ml. How many ml do you give to the patient? Give your answer to 3 decimal places where necessary.

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[[0]] ml

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