Question 984758
I want the standard deviation, which is sqrt (variance)=sqrt(240)=15.49
;
The fastest 95% of the motorists will have a z-score greater than or equal to 1.645.
z=(x-mean)/sd
1.645=(speed-average/sd
1.645=(x-120)/15.49
multiply both sides by 15.49
26.14=x-120
x=146.14 km/h or faster than 147 km/h rounding upward.