Question

A police radar unit is set up to monitor
vehicles on a stretch of highway with a
speed limit of 100 km/h. Long-term records
for this location show that speeds vary
normally with a mean of 105 km/h and
a standard deviation of 7 km/h. Drivers
who exceed the speed limit by 20 km/h
accumulate demerit points as well as pay
a fine.
a) What percent of the drivers will
accumulate demerit points?
b) What is the probability that a given
vehicle has a speed between 99 km/h
and 101 km/h?

Answer 1

Your question is perfectly suitable to use:
http://davidmlane.com/normal.html

enter 100 for mean
7 for sd
enter 120 in "above" and press enter to get .0161

I am sure you can figure out what to do for b)

Answer 2

Hi Reiny, Thx .... If I want to use the regular formula .....