15 : 5 " X : 500 

 5X = 7500 



X = 1 500 pounds of 23% cream. 

 Proof: 



The 2000 pounds of 18% cream will contain 360 pounds of fat 

 (2000 X -18 = 360). According to our results, the 2000 pounds of 

 1 8% cream is made up of 500 pounds of 3% milk and 1500 pounds of 

 23% cream. The 500 pounds of 3% milk will contain 15 pounds of 

 fat (500 X .03 = 15). The 1500 pounds of 23% cream will contain 

 345 pounds of fat, 345 + 1 5 = 360 pounds of fat, which is the number 

 of pounds in the mixture. 



In the original method of working problems in standardization all 

 computations are made on a pound basis. From this basis it is easy 

 to compute the amount of different materials needed to make up any 

 given quantities of milk or cream. Problems are worked by this 

 method as follows: 

 Problem 3. 



How much 23% cream must be mixed with 500 pounds of 3% milk 

 to make a mixture testing 18%? 



One pound of 23% cream will contain .23 pounds of fat. 

 One pound of 3% milk will contain .03 pounds of fat. 



The difference is 20 pounds of fat. 



Every time one pound of .23% cream is removed and a pound of 

 3% milk substituted there is removed .20 pounds of fat. 

 One pound of 23% cream contains .23 pounds of fat. 

 One pound of 18% cream contains .18 pounds of fat. 



The difference is 05 pounds of fat. 



It is desired to reduce the fat content .05 pounds of fat for every 

 pound of the mixture. This is done by the addition of 3% milk 

 which may in this case be regarded as a reducing agent. Since the 

 substitution of a pound of 3% milk for a pound of 23% cream reduces 

 the fat content of a pound mixture .20 pounds of fat and it is desired 

 to reduce the fat content .05 pounds of fat, it will require as much 

 of the 3% milk as .20 is contained into .05 or .25 (.05 -r- .20 = 25). 

 The .25 is the number of pounds of 3% milk there would be in one 

 pound of an 1 8 % mixture . The remainder . 7 5 pounds (i .25 = .75), 

 would be 23% cream. The following simple proportion will give the 

 number of pounds of 23% cream which must be added to 500 pounds 

 of 3% milk to make a mixture testing 18% fat. 



