The answer would be: 5 times lower than 0.100 M solution
To titrate an acid, you need a solution that can produce OH- ion so it can neutralize the H+ ion. The amount of OH- ion will be affected by the concentration and volume of the solution.
Since the solution is changed into 0.5M NaOH which was 5 times higher concentration than 0.1M NaOH, the volume needed to neutralize the acid would be 5 times lower.