The energy required to accelerate a car from $10m/s$ to $20m/s$ is how many times the energy required to accelerate the car from the rest to $10m/s$:

Energy required to accelerate from $10m/s$ to $20m/s$ $E_1=\frac{1}{2}m(400-100)$

Energy  required to accelerate from rest to $10m/s$  $E_2=\frac{1}{2}m(100-0)$

$\frac{E_1}{E_2}=\frac{\frac{1}{2}m(300)}{\frac{1}{2}m(100)}=3times$