If you are unable to complete the experiment at home- please don't worry!
Have a go at this:
Place these surfaces in order of slowest to fastest. So, the slowest surface, is the one that the car would travel the slowest down the ramp so in the longest amount of time. The fastest surface, is the surface that would allow the toy to travel the fastest down the ramp so in the least amount of time.
Order the surfaces from slowest to fastest: