I'm able to do the following problem:
In a road, the speed limit is $80$ km/h. The car speeds follows normal distribution and has average $70$ km/h and standard deviation $6$ km/h. How many percent of cars has speed more than $80$ km/h.
But how can I solve this one?
In a road, the speed limit is $80$ km/h. The car speeds follows normal distribution with average $a$ satisfying $69.5 <a<70.5$ km/h and standard deviation $s$ satisfying $5.5<s<6.5$ km/h. How many percent of cars has speed more than $80$ km/h.
A reasonable thing to do, since we are given a range of values for the mean and standard deviation, is to give the answer also as a range of values. The smallest percentage over $80$ is obtained by taking $\mu.69.5$ and $s=5.5$. The largest percentage is obtained by taking $\mu=70.5$ and $s=6.5$.