The speed is normally distributed with mean μ=63 and standard deviation σ =10.
Use the transformation [tex] \frac{X-\mu}{\sigma} [/tex] for calculating the probability. This value is called Z-score.
The Z score is [tex] Z=\frac{79-63}{10} =1.6 [/tex].
Refer to the standard normal distribution table.
The probability
[tex] P(X>79)=P(Z>1.6)=1-P(Z<1.6)=0.0548
[/tex]
Thus, [tex] 5.48\% [/tex] of the cars are travelling faster than 79 mph.
