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 W, in gallons, that must be purchased in order to measure out the portions needed for the mixture?
Choose the correct choice from the following.
A) 2  B) 2 1/2  C) 3  D) 3 1/2  E) 4
Given W:B = 3:5   That means say 3 gallons of white paint + 5 gallons of black paint = 8 gallons of paint mixture.   But we want least amount of whiteblack paints for minimum of 2 gallons of mixture, so lets reduce keeping same ratio,   1.5 : 2.5 gives  1.5 + 2.5= 
<gadget id="calculator"> 1.5 + 2.5</gadget>
<output>4</output>
4 gallons of mixture, but we want only 2 gallons, lets further reduce   0.75: 1.25 gives  1+1.5= 
<gadget id="calculator"> 1+1.5</gadget>
<output>2.5</output>
2.5 gallons of mixture. This looks ok, but lets reduce further just to be sure   0.375: 0.625 gives  0.5 + 1= 
<gadget id="calculator"> 0.5 + 1</gadget>
<output>1.5</output>
1.5 gallons of mixture, thats less than 2 gallons of mixture, so not acceptable.   So correct ans is 2.5 gallons. 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 W, in gallons, that must be purchased in order to measure out the portions needed for the mixture?