To a police investigator, skid marks evidence is extremely important in determining how vehicles moved in a collision. skid marks are the equivalent of fingerprints in a criminal investigation, and just as important. the speed a car was traveling can be calculated using the skid marks made as the car came to a stop. the formula for finding the speed of the vehicle is: s equals square root of 30 times d times f times n end root where: s = speed in miles per hour 30 = a constant value used in the equation d = length of the skid marks in feet f = drag factor for the road surface n = braking efficiency as a percent a car skids to a stop, leaving four skid marks with an average length (d) of 60 feet. the road is asphalt. skid tests reveal a drag factor(f) of 0.75. since all four wheels were braking, the braking efficiency (n) is 100% or 1.00. to the nearest mile per hour, what was the car’s speed at the time of the accident. 40 34 37 30