Cowling's rule

`d=(D(a+1))/24`

where `d` = child's dosage

`D` = adult's dosage

`a` = age of child in years

a) `d=(D(a+1))/24`

`d=(75(11+1))/24`

`d=(75(12))/24`

`d=900/24`

**d=37.5 mg**

b) `d= (D(a+1))/24`

`600 = (1000 (a+1))/24`

`600= (1000(a) +1000)/24`

`` `600/1=(1000(a)+1000)/24`

cross multiply

`600(24)=1(1000(a)+1000)`

`14,400=1000a +1000`

subtract 1000 from both sides

`13,400 =1000a`

`` divide each side by 1000

`13.4 = a`

``**The child is 13.4 years old. **

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