Consider the following Table :

Who is the fastest run scorer in the Test Match ?

Fastest run scorer means the batsman that has the best runs scored : balls faced ratio.

For batsman A: Runs scored: Balls faced = 75/175 = 0.43
For batsman B: Runs scored: Balls faced = 55/97 = 0.57
For batsman C: Runs scored: Balls faced = 35/125 = 0.28
For batsman D: Runs scored: Balls faced = 25/105 = 0.24

The best ratio is that of batsman B.