ARITHMETIC OF MILK AND MILK PRODUCTS 265 



the product containing C to be used, while C minus B 

 gives the pounds of milk (A) to be used or, expressed 

 in another way, the procedure becomes, B A=pounds 

 of product containing C to be used, and C B=pounds 

 of milk (A) to use. 



When the per cent, of fat in the normal milk is 

 to be decreased in the modified milk, the procedure is 

 thus indicated: A B_=zpounds of product containing 

 C to be used and B C=pounds of milk (A) to be 

 used. 



The simplicity of the method becomes readily ap- 

 parent when practically illustrated. 



(i) When the per cent, of fat in milk is to be in- 

 creased by addition of cream or richer milk. Rule. 

 From the per cent, of fat desired in the modified milk 

 subtract the per cent, of fat in the milk to be modified, 

 and the result is the number of pounds of cream or 

 richer milk to be used. From the per cent, of fat in 

 the cream or richer milk subtract the per cent, of fat 

 desired in the modified milk, and the result is the num- 

 ber of pounds to use of the milk to be modified. Ex- 

 ample: What relative amounts of normal milk and 

 cream must be used to produce milk containing 4.5 

 (B) per cent, of fat, when the normal milk contains 

 3.5 (A) per cent, of fat and the cream 25 (C) per 

 cent. ? 



A=3.s C B=2o.s (pounds of milk to use). 



B 4-5 



0=25 BYA=I (pounds of cream to use). 



Cream 



The results mean that 20.5 pounds of milk contain- 

 ing 3.5 per cent, of fat, mixed with i pound of cream 

 containing 25 per cent, of fat, will produce a modified 



