Mixture A is 30 percent alcohol, and mixture B is 60 percent alcohol. If the two are poured together to create a 4-gallon mixture that contains 40 percent alcohol, approximately how many gallons of mixture A are in the mixture?
Options
A) 0.8  B) 0.7  C) 0.6  D) 0.5  E) 0.4
(60-50)/(50-30) = Qa/Qb   10/20= Qa/Qb   1/2 = Qa/Qb   Qa = (1/6) * 4 = 4/6 = 1/2= 
<gadget id="calculator">1/2</gadget>
<output>1/2 = around 0.5</output>
0.50   Answer : 0.5
<result>D</result>
Mixture A is 30 percent alcohol, and mixture B is 60 percent alcohol. If the two are poured together to create a 4-gallon mixture that contains 40 percent alcohol, approximately how many gallons of mixture A are in the mixture?