Over this 10-minute interval, the car's average acceleration is
[tex]\dfrac{30\,\mathrm{mph}-20\,\mathrm{mph}}{10\,\mathrm{min}}=\dfrac{10\,\mathrm{mph}}{\frac16\,\mathrm h}=60\dfrac{\rm mi}{\mathrm h^2}[/tex]
The MVT says that at some point during this 10-minute interval, the car must have had an acceleration of 60 mi/h^2.
