Maths problem.. please help

devilgirls1

had test today with this equation..

c= (A+1) D
24

c- correct dose
D- adult dose
A- child

it said it was the Cowling medicine theory??

1. the question were if an adult takes 36mg what would be the correct dose for a 3 year old

2. if a child takes 10mg whats the correct dose for an adult..


i failed the test by 2 points and will be re-taking next week but would appreciate some help in solving the equation.... or if anyone can point me in the right direction cos ive been on gcse bitesize but cant find it anywhere..

please move if in wrong place..

TIA

Broke_Student

I've forgot my maths and can't figure it out! It doesn't look right to me at first looks - if the entire equation is divided by 24 then you can just ignore the 24 right? And I don't see how there are three unknown values but only one of them is given in the second question.

I will delete this post once a maths boff makes me look stupid

dmg24

Do you mean

c = ((A+1)D)/24 i.e. only one side is divided by 24?

Also, is A the age of the child? If so, then the second part of the question cannot be answered.

Edit: Just Googled 'Cowling(s) Medicine Theory' - not getting any results!

HalibutMadness

I think it must be the RHS divided by 24. But I'm not sure threadstarter has the right letters for the right thing. I think A must be age of child. If that is correct, then:

C = (3+1) x 36/24

But then part b still doesn't make sense.

dmg24

Found it - Cowling's Rule:

An obsolete rule for a child's dose: that fraction of the adult dose obtained by dividing the age of the child at the nearest birthday by 24

c = ((child's age + 1)/24) x (adult dose)

c = 4/24 x 36 = 6 mg

10 = ((child's age + 1)/24) x (adult dose)
240/(child's age + 1) = adult dose*

* cannot give final answer without knowing age of child

devilgirls1

thankyou everyone.......

dmg24- there was definatly no child age on the second part of the question but the first part i did exactly how you have..

dmg24

Just state it with the letters still in if that is the case, maybe they were trying to catch people out by doing that?

Examiners are one breed I have never been able to figure out! x

beckiem

omg total confusion i thought i used to be pretty good at maths but obviously not

Voyager2002

devilgirls1 wrote: »

thankyou everyone.......

dmg24- there was definatly no child age on the second part of the question but the first part i did exactly how you have..

Maybe it is still the same child as in the beginning of the question, in which cases/he is probably still 3 (unless you are a very slow worker!).

daveyjp

I don't think you need the child's age - its a 2 part question which will involve manipulation of the original equation to get the child's age first i.e. state the equation in terms of A.

22 years since I did 'O' level maths (grade 'B'!), but if I've remembered correctly:

A=(24c-D)/D

dmg24

Did you mean to have D in there twice daveyjp? Have you used the same letters as in the original question?

c- correct dose
D- adult dose
A- child

The second part of the question refers to 'a child' not 'the child' (i.e. the child referred to in part a).