A car of mass 1350 kg moves at 54 km/h. What is its kinetic energy? …

Step 1. Kinetic energy. $K = \tfrac12 \times 1350\ \text{kg} \times (15\ \text{m/s})^2 = 151875\ \text{J}$, about $1.52 \times 10^{5}\ \text{J}$.

Step 2. Twice the speed. $K$ grows by $2^2 = 4$: $4 \times 151875\ \text{J} = 607500\ \text{J}$.