please help with normal distribution

Question

The Vehicle Speeds at a certain location in PLUS highway can be described by a normal distribution. The mean speed is 110 km/h, and the standard deviation is 10 km/h. Find the percentage of vehicle speeds at this location which are faster than 123 km/h.

Answer 1

123 kph's z-score is (123-110)/10 = 1.3 

so area under standard normal distribution curve up to z=1.3 is 0.90320.

 

This means 90.32% are below 123 kph, leaving 9.68% faster than 123 kph.