问题
单项选择题
A certain shade of gray paint is obtained by mixing 3 parts of white paint with 5 parts of black paint. If 2 gallons of the mixture is needed and the individual colors can be purchased only in one-gallon or half gallon cans, what is the least amount of paint, in gallons, that must be purchased in order to measure out the portions needed for the mixture ？（）
A.A
B.B
C.C
D.D
E.E
答案
参考答案：B
解析：
根据题意可设需要白色颜料3x加仑，需要黑色颜料为5x加仑来配出2加仑的混合颜料：
3x+5x=2→x=0.25加仑，因此需要0.75加仑的白色颜料和1.25加仑的黑色颜料，而这些颜料只能以1加仑一筒或0.5加仑一筒的形式购买，所以需要买1加仑白色颜料和1.5加仑的黑色颜料，共2.5加仑。