Question 980517


Let us find the circumference  (the length of the circle)  of the radius  r = 18 inches.

It is   {{{2*pi*r}}} = 2*3.14*18 =  113.04 inches.


So,  when the wheel of the truck makes one rotation  (one revolution),  the truck moves  113.04  inches ahead.

When the wheel of the truck makes  500  rotations,  the truck moves  500*113.04 = 56520  inches ahead.  It is  {{{56520/12}}} = 4710 feet.


So,  the speed of the truck is  4710 feet per minute. 

It is  4710*60 = 282600 feet per hour,  or  {{{282600/3}}} = 94200  yards per hour.  (Reminder:  1 yard = 3 feet). 


Now, &nbsp;to convert this speed to miles per hour, &nbsp;we need to divide the value of &nbsp;94200&nbsp; by &nbsp;1760, &nbsp;because &nbsp;1 mile = 1760 yards &nbsp;(see the &nbsp;<A HREF=https://en.wikipedia.org/wiki/Mile>article</A>&nbsp; from Wikipedia). 


In this way you get the speed of &nbsp;{{{94200/1760}}} = 53.52 {{{mi/h}}}.


<B>Answer</B>. &nbsp;The speed of the truck is &nbsp;54 {{{mi/h}}} &nbsp;(approximately).