In what ratio should a 20% methyl alcohol solution be mixed with a 50% methyl alcohol solution so that the resultant solution has 40% methyl alcohol in it?	Pick.
A) 1 : 2
B) 2 : 1
C) 1 : 3
D) 3 : 1
E) 2 : 3
Explanatory Answer   Let there be 1 litre of the solution after mixing 20% methyl alcohol and 50% methyl alcohol..   If the concentration of methyl alcohol in it is 40%, then 0.4 litres of the resultant mixture is methyl alcohol.   Let x litres of the solution containing 20% methyl alcohol be mixed with (1 - x) litres of the solution containing 50% methyl alcohol to get 1 litre of the solution containing 40% methyl alcohol.   X litres of 20% methyl alcohol solution will contain 20% of x = 0.2x litres of methyl alcohol in it.   (1 - x) litres of 50% methyl alcohol solution will contain 50% of (1- x) = 0.5(1 - x) litres of methyl alcohol.   The sum of these quantities of methyl alcohols added up to the total of 0.4 litres in the resultant mixture.   Therefore, 0.2x + 0.5(1 - x) = 0.4 litres   0.2x + 0.5 - 0.5x = 0.4   0.5 - 0.4 = 0.5x - 0.2x   x = 0.1/0.3 = 1/3 litres   And 1 - x = 1 - 1/3 = 2/3 litres.   So, the two solutions are mixed in the ratio of 1 : 2.   correct choice is (1 : 2)
<result>A</result>
In what ratio should a 20% methyl alcohol solution be mixed with a 50% methyl alcohol solution so that the resultant solution has 40% methyl alcohol in it?