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?
Options:
A) 2  B) 2 1/2  C) 3  D) 3 1/2  E) 4
Ratio; white: black: gray = 3: 5: (3+5) = 3: 5: 8   If 2 gallons of the mixture is needed &lt;==&gt; Need 2 gallons of gray paint.   Then,   3: 5: 8 = x: y: 2   3/8 = x/2; x = 3/4   5/8 = y/2; y = 5/4   You need 3/4 gallon of white. You have to buy 1 gallons.   You need 5/4 gallons of black. You have to buy 1 gallon and another 1/2 gallon of black.   The least amount of paint = 1 + 1 + 1/2 = 2.5.   ANSWER:2 1/2
<result>B</result>
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?