If 5% of all vehicles travel less than 39.15 m/h and 10% travel more than 73.23 m/h, what are the mean and standard deviation of vehicle speed

Standard deviation = 11.30 m/h

Mean = 57.74 m/h

Step-by-step explanation:

Assume that the travel speed is normally distributed.

The corresponding z-score to the 5th and 90th percentile of normal distribution are, respectively, -1.645 and 1.282.

For any given speed X, the z-score is:

If z = -1.645 for X = 39.15 and z= 1.282 for X=72.23, the following system can be solved for the mean and standard deviation of vehicle speed:

The standard deviation is 11.30 m/h and the mean is 57.74 m/h.

i do not know this sorry : (