Three grades of milk are 1 percent, 3 percent and 2 percent fat by volume. If x gallons of the 1 percent grade, y gallons of the 2 percent grade, and z gallons of the 3 percent grade are mixed to give x+y+z gallons of a 1.5 percent grade, what is x in terms of y and z?  Select.
A) y + 3z
B) (y +z) / 4
C) 2y + 3z
D) 3y + z
E) 3y + 4.5z
Soln:   The resulting equation is   =&gt; (.01x + .03y + .02z)/(x+y+z) = 1.5/100   =&gt; x + 3y +2z = 1.5x + 1.5y + 1.5z   taking x to one side and y and z to other side we get   =&gt; x = 3y + z   Ans is 3y + z
<result>D</result>
Three grades of milk are 1 percent, 3 percent and 2 percent fat by volume. If x gallons of the 1 percent grade, y gallons of the 2 percent grade, and z gallons of the 3 percent grade are mixed to give x+y+z gallons of a 1.5 percent grade, what is x in terms of y and z?