<PRE><B>Question 252107</B>
ans:27

since the prob. of choosing a red marble is 2/5.

if there are are 20 red marbles then there should be 50 marbles overall.
but they should be less than 50

so if there are 19 red then there should be 47.5(for 2/5 prob) marbles which is not possible as it is not an whole number

so if there are 18 marbles then there will be 45 marbles overall and the no of white marbles will be 27 which is the maximum possible.</PRE>