# Nursing math questions

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by Drake2400 (New)

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I have a couple of questions about calculating dosage questions in children. First example is a order for amoxicillin 50mg per kg per day PO q12 hr x 5 days for strep throat patient weighs 60 lbs available is 400mg per 5 ml, max dose is 500mg per dose how many ml will the child receive per dose? This patient would need the max dose which would be 6.25 ml per dose, I was taught to round to nearest tenth which would be 6.3ml  if dose volume greater than 1 ml. but does this apply if max dose is calculated to the hundredth of an ml?

the next question MD orders Ceftriaxone 50mg per kg IM to be administered in 2 separate injections for a child with otitis media patient weighs 21 lbs available 350mg per ml, how many ml per dose should be given? I completed the calculation using DA and come up with 1.3636 ml before dividing it into 2 separate injections. Should 1.3636 ml be rounded to 1.4 ml then divide or leave it and round the final calculation which I came up with 0.68ml per injection

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dianah has 45 years experience as a ADN and specializes in Cath Lab/Radiology.

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Moved to Nursing Student Assistance area.

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3 hours ago, Drake2400 said:

... I﻿ was taught to round to nearest tenth which would be 6.3ml  if dose volume greater than 1 ml. but does this apply if max dose is calculated to the hundredth of an ml?

[...]

Regardless of how many decimal places you use when you calculate the volume, the limiting factor is going to be the graduation marks on the syringe you're using. All 3 - 10/12 mL oral syringes  am familiar with are graduated in 0.1 mL increments.  While you could could estimate a volume to 0.05 mL, anything other than this would be difficult.

4 hours ago, Drake2400 said:

[...]

... Should﻿ 1.3636 ml be rounded to 1.4 ml then divide or leave it and round the final calculation which ﻿﻿I came up with 0.68ml per injection

I complete all calculations, and then round the final answer.

Best wishes.

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How it worked at my school, we didn't really consider the syringe that would be used unless it was given in the question. We just calculated the dosage, and then we rounded according to the rounding rules we were given. But, I can't ever think of an instance in school where they had us calculate to the hundredth of a mL. There might of been one, I just don't remember . Is there a specific reason you're asking since you were told to round to nearest tenth?

Like chare said, when I was in school, I completed all my calculations and then I rounded the final answer. However, you could ask your instructor what he/she prefers - you rounding at the end or you rounding as you go.