This activity is designed to teach problem solving. The standard size marking on a tire is used to determine the tire’s diameter by applying ratios and unit conversions. The diameter is used to determine the tire’s circumference. Part I: The aspect ratio is part of the size markings on a tire. The student will use this information along with two other pieces of information from the tire marking to computer the overall diameter of various tires. Part II: The diameter is used to compute the circumference of a tire. The circumference is used to determine the number of revolutions required to travel a particular distance. The student will practice rounding in both parts of the activity.