Framing of Formulae


   
 
Change of subject of formula
In the formula I is called the subject of the formula.
 
To make 'P' the subject of the formula:
 
P x T x R = 100 x I
 
 
 
If make 'a' the subject of the formula.
 
 
m(a + b) = a Cross multiplying.
 
am + bm = a
 
am -a = - bm Take terms containing 'a' to one side.
 
a(m - 1) = -bm remove 'a' as a common factor.
 
 
[Note: Sign is changed in both the numerator and the denominator]
 
 
 
If make 'y' the subject of the formula.
 
 
Squaring both sides
 
ma2 = xy
 
i.e.,
 
 
It is given that
 
(i) Make b the subject of the formula.
 
(ii) If a = 9 and R = 3, find b.
 
 
(i)
 
 
 
(Invertendo)
 
[Note: Invertendo means inverting the ratios.]
 
(ii)
 
 
 
     
   
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