Answer
The change in speed from 15 m/s to 20 m/s results in a greater change in kinetic energy.
Work Step by Step
We know that $K=\frac{1}{2}mv^2$.
A change in speed from 10 m/s to 15 m/s results in $\Delta K=\frac{1}{2}m(15^2-10^2) = 62.5m$.
A change in speed from 15 m/s to 20 m/s results in $\Delta K=\frac{1}{2}m(20^2-15^2) = 87.5m$.
