A professional gambler has won 40% of his 25 poker games for the week so far. If, all of a sudden, his luck changes and he begins winning 80% of the time, how many more games must he play to end up winning 60% of all his games for the week?
Pick
A) 20  B) 25  C) 30  D) 35  E) 40
Initially the person has played 25 games with probablity of winning as 40%   Thus, number of games won = 10   Later when the probability of winning changes to 80% and assuming x games were played by him:   Total number of win, 60% of all games =0.6(x+25)=10+0.8x=0.6(x+25)=10+0.8x   0.2x=50.2x=5   x=25 x=25   so, he has to play 25 games.   Alternatively, this could be solved by allegation method.   25 = 25games ;ANSWER:25
<result>B</result>
A professional gambler has won 40% of his 25 poker games for the week so far. If, all of a sudden, his luck changes and he begins winning 80% of the time, how many more games must he play to end up winning 60% of all his games for the week?