Let the average diameter of the automobile tire is about 2 feet. Therefore its circumference is [tex]2 feet\times \pi =6.29 feet[/tex].
Now we have to convert an automobile tire is rated to last for 60,000 miles in to feet.
As [tex]1 miles =5280 feet[/tex] .
So, [tex]60000 miles = 60000\times 5280 feet =316800000 feet[/tex]
Thus the number of revolutions,
[tex]\frac{316800000 feet }{6.29 feet} =50365659.8 revolutions \\\\=5.0\times10^7 rev[/tex]
Hence, order of magnitude of revolutions is 7.
