First, we need to convert all these into the x/20 fraction. Multiply 1/10 by 2/2, and get 2/20, and 2/5 by 4.
Our new fractions are:
2/20
8/20
7/20
If we add all these together, we get 17/20.
The remaining time is 20/20 minus 17/20, which gives us 3/20.
3/20ths were used for sprinting.