Three grades of milk are 1 percent, 2 percent, and 3 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 ? 1 Y+3Z 2 Y+3 / 4 3 2Y+3Z 4 3Y+Z 5 3Y+4.5Z 答 1 一直搞不懂……. |