How do rockets attain high speeds?

The equation relating velocity of a rocket to it's mass is given by v1-v2 = uln(m1/m2), where v1, m1 and v2,m2 are masses and velocities at some times t1 and t2.

Assuming a fuel mass to rocket mass ratio of 99 : 1, we get final velocity to be only 2.3 times the initial velocity. How then do rockets attain speeds of over 10000 mph?

This is a question asked in Morin's Classical Mechanics text. Any help?