Math Is Fun Forum

Monique

Member

Registered: 2007-02-17

Posts: 22

Clark's rule

In calculating how much of a certain medicine to give to a child, a formula called Clark's rule is sometimes used.

C = wa/70               where C represents the dosage required for the child,  w represents the
                               weight of the child in kg, and a represents the adult dosage.

a)    Find the dosage for a given medicine for a 20 kg child, where the adult dosage was 15mL.
   
b)   Calculate the adult dose if you know that a 40 kg child recieved 8 mL.

Thanks so very much this makes so much of a difference helping my young child with her homework. Never quite completed high school maths and feel so silly when trying to help my child out so having some idea with the "how" provided by you wonderful people makes a significant difference

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 48,410

Re: Clark's rule

a) C = wa/70 = (20 x 15)/70 = 300/70 = 30/7 = 4.29 ml.

b) 8 = 40a/70 => 70 x 8 = 40a
=> a = (70 x 8)/40 = 14 ml.

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