Il6 DAIRY TECHNOLOGY 



The following formula may be used when the percentage 

 is a convenient number to work with: Divide the per 

 cent of fat in the milk that is desired by the per cent of 

 fat in the milk on hand. The result will be the per cent 

 of the milk on hand to be taken. The remaining per cent 

 of milk will be the skim milk to be used. 



The correctness of the graphical illustration, Fig. 27, 

 may be proven as follows: 



Let p be the per cent of fat in the cream of the richer of 

 the two milks. 



Let q be the per cent of fat in the milk of the poorer of 

 the two milks. 

 Let r be the per cent of fat required, 



X be the quantity of richer milk required, 

 y be the quantity of thinner milk required. 



Then px is the fat in the richer milk for new mixture, 

 qy is the fat in the poorer milk of new mixture, 

 (x + y) is quantity of new mixture, 

 r {x-\- y) is the fat in new mixture, 

 px + qy is the fat in new mixture. 

 Therefore, px -\- qy = r {x + y). 

 Solving, px + qy = rx + ry. 



px — rx = ry — qy. 

 x(p — r) = y{r — q). 



Then dividing both sides of the equation hy y (p — r) 

 we have 



X _ r — q 

 y p —r 



Substituting with figures from the above example we have 



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